PB82-243981
     Noise Effects Handbooks
     A Desk Reference  to  Health and
     Welfare Effects of Noise
     (U.S.) Environmental  Protection Agency
     Washington, DC
     Jul 81
UH Departmsnf of Commerce
      Technical Information Service

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EPA
                                          EPA 550/9-82-106
          NOISE  EFFECTS HANDBOOK:


     A Desk Reference to Health and Welfare

              Effects of Noise
      By Office of  Che Scientific Assistant
      Office of Noise Abatement  and Control
      U.S. Environmental Protection Agency
         October 1979, Revised July 1931

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REPORT DOCUMENTATION >• REPORT NO. 2.
PAGE EPA 550/9-82-106
4.
7.
9.
12
IS
Titli and Subtitle
NOISE EFFECTS HANDBOOK: A DSEK REFERENCE TO HEALTH
AND WELFARE EFFECTS OF NOISE
Author<>)
Performint Organization N«m« and AddreH
SCIENTIFIC ADVISOR'S STAFF
EPA/ONAC
. Spontorln« Organization Name and Addntu
ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF NOISE ABATEMENT AND CONTROL
WASHINGTON D.C. 20460
3. RtclpUnf 1 Accession No.
?B!!2 24398 1
i. Report Data
JULY 1381
c.
>. Performing Onfanlzatlon Rapt. No.
10. PTTj|act/T.«l./Work Unit No.
11. Contract(O or Grant(G) No.
. Oaacrtptorm
                 NOISE  ABATEMENT
                 NOISE  CONTROL
                 HEALTH &  WELFARE EFFECTS  OF NOISE
                 EFFECTS OF NOISE
    b. Idafftlflart/Opan-Cndaxl Tarmt
    c. COSATI fleld/Oroup
11. AvillaWlrty *t*tam«f<;
NTIS
NANCO
1». Security Cla*a (TMi Maoort)
UNCLASSIFIED
a WWoMMS>C*f)
21. No. of r««w
130
22. Price
(SeeANSl-IM.lt)

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 DESK REFERENCE


 TO HEALTH & WELFARE  EFFECTS  OF NOISE


                 TOPICAL OVERVIEW  (SEE ALSO INDEX, SECTION 12)
 1.    The  National  Moise Problem

 2.    Hearing   Loss;     normal   auditory   function,   hearing  .loss  criteria,
      presbycusis,  hearing conservation, hearing impairment formulas

 3.    Nonauditory  Physiological  Response:   stress,  arousal  response,  cardio-
      vascular  effects, effects on  the  fetus
 4.    Communication  Interference:   factors  that   affect  speech interference,
      masking,  measurement  of masking  and  speech  interference,   levels  and
      criteria,  special populations, overcoming speech interference

 5.    Performance Interference:   detriments of interference;  qualities of noise
      and  their relationship to performance  interference; noise-sensitive tasks;
      effects on children; positive effects; and injury rates
 5.    Sleep  Disturbance;   falling asleep,  awakening,  arousal and sub-awakening
      effects;  criteria; noise  and  non-noise factors; other considerations

 7.    Subjective  Response:   (individual,   psychological   responses):   special
      populations,  coping  behavior, antisocial  behavior,  decrease  of helping
      behavior

 3.    Community Response;   criteria,  activity   interference,   predictors   of
      community annoyance,  relation   to   population  density,  urban  survey
      findings

 9.    Health  and  Welfare  Analysis:  how  i:  is   carried  out  in  regulatory
      development;  fractional  impact;  level-weighted  population
10.    Summary of Hunan Effects of "oise fiora Various Outdoor Noise Levels
11 .    References

i;.    Index

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THE NATIONAL NOISE PROBLEM
Since  1973,  Che  Department  of Housing  and  Urban Development  (HUD)  (39)*  has
conducted an Annual Housing Survey for the Census  Bureau in which noise has been
consistently ranked as a leading cause of neighborhood dissatisfaction.  In fact,
nearly  one-half  of the respondents each  year  have  felt  that  noise  was  a major
neighborhood  problem  (see Figure  2-1).   In the  1975  survey,  street  noise  was
mentioned  more often  than  all other  unwanted neighborhood  conditions.   This
survey  has  also  shown  that  aircraft  and traffic noise are  leading  factors  in
making  people  want to move from their  neighborhoods.  Approximately one-third of
all  the respondents  who wished  to move  because of  undesirable  neighborhood
conditions, did so             because of noise.   (39)
                  HEAVY TRAFFIC  "is
                  STREET REPAIR 21:
?
                   FIG. 1-1.  ^DESIRABLE NEIGHBORHOOD CONDITIONS
                              FOR HOMEOVNKRS AMD 3ENTZRS:  U7IITSD
                              STATES COMPAS.XTIVE RANKING, 1975.
                              SOURCE:  Ref. 4, pp. 3-12.
  References are listed in Section  11, e.g.:  (Ref. 39).
                                         1-1

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Both a  poll  conducted  by the Gallup Organization  in  November 197S for the National
     League  of  Cities  and  a  Harris Survey  for  the  ABC network  in  January 1979  on
     attitudes toward environmental issues      indicated that the  public views noise
     as a growing problem warranting more governmental attention and action.
     How  aany  people are  estimated  to live in  residential  areas  with noise  levels
     above recommended limits?

     According  to  the Levels Document, the day-night sound  level  of residential areas
     should not exceed 55  d3 to  protect  against activity  interference and annoyance
     (5).   It  is  estimated that well  over  100  million people,  nearly half  the  U.S.
     population, live in  areas  where  the  noise  exceeds this level (see Figure 1-2).
     Twelve million people  are estimated  to  live in  areas where  the  outdoor  L,
     -v
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                                               ^V—Total
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               ^-Aircraft :
                    ncrement:
                                       Urban Noise-
Freeway Increment
                                       I
                         30    40
50    60
   dn
               70
80    90
          FIG.  1-2.   RESIDENTIAL NOISE ENVIRON>EN'T OF THE NATIONAL
                      POPULATION AS A FUNCTION OF EXTERIOR DAY-NIGHT
                      AVERAGE SOUND LEVEL.
                      SOURCE:  Ret. 5
What  is  the  JQSC pervasiva enviroanental  aoisa  source  and how many oeoole  are
exposed  to ic?


As  shown in  Table   1-1,  urban traffic  is by  far the  aost  pervasive  outdoor
residential  noise  source, although  aircra.ft  noise is  a significant source  as
                                         1-3

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well.  Over  96  nil lion persons are estimated  to be exposed, in and around Cneir
homes, Co undesirably high traffic noise levels exceeding Ldn > 55 dB.  Figures
contained in Table 1-1 for each source  represent the number of people exposed at
or above  a  given level (L, )  for  the  source  in  question and do  not  take into
                          dn
consideration that an individual may be simultaneously exposed to more than one
source culminating in a higher total exposure.

L
dn
(dB)
80
75
70
65
60
55
Number of People in Millions for Each Noise Category

Urban
Traffic
0.1
1.1
5.7
19.3
46.6
96.8
Aircraft
0.1
0.3
1.3
4.7
11.5
24.3
Rail
_
-
0.8
2.5
3.5
6.0
Industrial
_
-
-
0.3
1.9
6.9
       TABLE 1-1.  SUMMARY OF THE NUMBER OF PEOPLE EXPOSED TO VARIOUS
                   LEVELS OF L,  OR HIGHER FROM NOISE SOURCES IN THE
                              dn
                   COMMUNITY'.
                   SOURCE:   Re f.  7
What are typical noise exposures for people throughout the day for various U . S .
life styles?
This information is not  precisely  known.  However a study by Schori seems  to  show
an average exposure of L  ,,4) » 75 d3.  However, his sample is not necessarily
typical (8).

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How  many  workers  and  non-workers  are  exposed  tc  noise  levels  which  nay  be
damaging to their hearing?

An estimated  15 million  American  workers  are exposed Co an L   ,„.. of 75 dB or
                                                             aq (a;
above which may be  hazardous  to thsit hearing.   Because of the overlap between
persons in occupational and non-occupational noise exposure  situations, there is
an estimated  total  of  20  to  25 million persons  who may possibly incur hearing
losses based  on an  L   ,„, of 75 d3 or  above (7).
                    eq (8)
What Alight be considered  the typical daily noise exposure pattern?

Figure  1-3 hypothetically  depicts an  example of  what  might be  considered a
typical daily noise exposure of a  homemaker, students, and workers.
                                         1-5

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    90
    80
    70
I   50
   40
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                                   Factory
        Urban
        Environment
       Suburban
       Environment
                                                *  •
                                                L
        Play Outside, Shoo
             (Urban)

        Play Outside, Shop
           (Suburban)

        Work. Play in Home
                                 Classroom
                                   Office
3

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     12      3
  Midnight
     0       3
                            ifmH&
                                       K gii;<
      9      12
            Noon
      9      12     15
                                                  18
     9      12
        Midnight
     9      24
           FIG.  1-3.   HYPOTHESIZED  LIFE  STYLE

                        WISE EXPOSURE PATTERNS.
                                   1-6

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HEARING  LOSS
NORMAL HEARING
How does  the hunan ear work?
The Figure  2-1 shows a schematic diigram of how the hunan ear functions,
             FIG. 2-1.  A SCHEMATIC DIAGRAM OF HOW THE HUMAH
                        EAR FUNCTIONS
                        Sourca:  Ret. 11
The outer  ear  consists of the auricle  or  pinna  [1  not  shown]  and the auditory
canai  [21.  Tha pinna of the hunan ear is a residual structure although  it aav aid
in the localization of  sound entering the ear.  The sound wave entering  the ear is
enhanced by  resonant  characteristics  of  the  auditsry  canal  (12).*  Sound
waves  travel up  the auditory  canal  [2J  and  set  up vibrations ir. the eardrun or
tympanic -aerabrane  (3 J.

* References are  listed in Section  15, e.g.:  (Ret. 12).
                                        2-1

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Behind the tympanic membrane is a cavity called the middle ear.  The middlo ear
functions as  an  impedance matcher.*   Specifically,  sound pressure  from waves
traveling through the air (low Impedance)  is  amplified about 21 times so that it
may efficiently  travel  into  -lie high impedance fluid medium  in  the inner ear.
This is accomplished by the leverage action of the three middle ear bones:  the
malleus,  incus, and stapes [4].   The footplate of  the stapes,  in turn, moves in
and out of the oval window [5l.

The movement  of  the  oval  window sets  up motions  in Cha  fluid  [6] that fill the
inner ear or  cochlea.  Movement of this  fluid causes  the hairs  that are immersed
in fluid to move [7].  The movement of these  hairs  stimulates  the calls attached
to  them  to  send impulses  along the  fibers  of the auditory  nerve   [8] to the
brain.  The  brain translates  these  itnnulses into the sensation of  sound.  (12)
'•mat is considered to be normal hearing?

The ability to hear means being capable  of  detecting  sounds within the  frequency
range of 15-20,000 Hz.  The threshold of audibility or  the  point  at which sounds
are baraly detectable  is  shown in  Figure 2-2.   In clinical hearing assessment,
normal hearing falls within a range of 0  to 25 d3 of the threshold of audibility.
Impedance is comprised  of  frictienal  resistance,  mass, and stiffness,  and  thus
acts in opposition to the incoming sound wave.

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               I 110
               r~i i Qf

               ° so

               T 60

               -j <0
               o
               2 20
               o.
               "?  o
                   20
                           100
                                   500
                                           2K   5K   10<
                                                    liequency Ht
                 FIG. 2-2.  AVERAGE THRESHOLD  OF  HEARING
                            Source:  Ref.  12,  p.  12.
At what  level  is  the  threshold  of  pain?

The  threshold of  pain  is located  at  trie upper  boundary  of audibility  and in
normal hearers is  in  the  region of 135 dB for  all frequencies (13).
Are there differences  in  normal  adult  hearing  based on sex?

Starting in  the early  taenage  years, and  particularly in the age range of 25 to
65, women i.i  industrial countries have batter hearing  than  do men.  However, the
rate of hearing loss in men  over 50 declines while  that  of  women of the same age
increases.   Above 75 years  of age  the difference  in  hearing  between the sexes
tends to become insignificant.  These differences most  likely exist because noise
exposure is primarily greater  for men due to the occupational noise they usually
encounter in  their early  and middle years  (14).
                                         2-3

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 Are  there  differences  in normal  adu_l_c  hearing based on age.

 The  threshold  of hearing rises (haring becomes less sensitive)  with  age.  This
 effect  involves  primarily,  and is most marked at,  the  higher  frequencies above
 3000 Hz (14).    Studies  of  large population  samples have  shown  thaC  this loss
 begins  at  around age twenty and increases with each decade  (13).   Refer to  Figure
 2-7  which  shows  curves  representing  changes  in  the average threshold  of hearing
 with age  for aales  and  females.   (Also  see  section on  Presbycusis. )

 Are  there  differences  in normal  adult hearing based on race?

 There is no inherent difference in hearing levels  between the races  that  make up
 the  population of the U.S.  Human ears  are essentially  the  same around the world.
 Any  demographic  differences  that  have   appeared  in  some  _studies   may  be
 attributable to  differing environmental noise exposures.   (15)

 How  is hearing measured?

 Hearing is commonly  measured  by  the  use of a pure-tone audiometer.   Test tones
 are  produced by  the audiometer at known  intensities  and  are  presented  to  the
 subjects'  ears  through  earphones.  This  is known as air  conduction testing.  Each
 ear  is tested separately  and  commonly  at  the following  test  frequencies:  250,
 500,   100:,  2000,  4000,  and  8000  Hz.    At  each   test  frequency,  the  hearing
                                                                     ~~Cf>
 threshold  for that test tone is  identified as  the  lowest level  of tone^which the
 subject  responds correctly at least  50  percent of  the  time (13).  Hearing level
 is reported  as  the difference  between the  sounr.  pressure  level (S?L)   of  the
measured  hearing threshold  for  the subject and  the  SPL  for  a "normal"  or
 "average"   subject  as defined  in Figure  2-2 on  page   2-3.     The results  are
plotted  on  an  audiogratn.   The  sample  audiogram  shown in Figure 2-3  reflects
hearing  level ranging from 45 dB at  250 Hz  to 25-35 dB at  8000  Hz.   Each  ear is
represented separately  (0 = right,  X  = left).   The modified brackets  indicate
bone  conduction  thresholds; (<= right, > =  left).
                                         2-4

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HEARING  LOSS
VhaC different types of hearing loss are there?
There are  Cvo  major  types  of hearing loss:  conductive and  sensori-neural .  A
conductive loss is usually  associated with  the outer or niddle ear.  This kind of
loss  is  usually  caused by a perforation or  infection in  the aiddla ear or  an
inf laoraat ion of th3 middle ear  bones.  This loss blocks transmission of  sound to
the cochlea or inner ear.  Conductive  losses  are correctable  by  surgery.

-------
 A sensori-neural  loss  results from damage to Che cochlea or  neural  structures  of
 the  ear.   Birth defects, noise, ototoxic drugs, fever, or trauma may cause  this
 type of loss.  Sensori-neural losses  are not medically correctable.   In addition,
 sensori-neural hearing loss  can  be  classified in several ways:  noise-induced,
 presbycusis,  sociocusis, or due to birth defects, congenital problems, disease,
 injury, or drugs.
 Hew  is  the  type  of hearing loss determined?

 If air  conduction  testing indicates that a hearing loss exists,- it is necessary
 to determine whether it is of the  conductive  or  sensori-neural  type through bone
 conduction  testing.   To do  this  a  bone-conduction  vibrator is attached to  the
 mastoid  process  of  the  skull just behind the ear.  Test tones are presented  at
 differing intensities just as with tones presented through earphones.  Again each
 ear  is tested separately.   Often a masking  tone has to be applied  to the untested
 ear  to  ensure  that responses are heard  only by the test ear.   If  the hearing
 threshold  determined by  bone  conduction  testing  is  essentially normal,   the
 hearing  loss  indicated  by air  conduction  is of  the  conductive   type.   If  the
 threshold  for  bone   conduction  is  consistent  with  Chat   determined  by   air
 conduction, the hearing loss is of the sensori-neural  type.   A  mixed loss exists
 if there is a sensori-neural  loss  with  a superimposed conductive loss. (16)

Can conductive losses be caused by noise?

Yes.   Rupture of the ear drum and  disturbance of the middle  ear bones can result
from a  very high amplitude  impulse  or blast.  This  is  often  called traumatic
hearing  loss.   The  maximum conductive loss  is usually around 50 to 60 dB.   (12)
                                         2-6

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What are some common causes of sensori-neural hearing loss in newborn babies?

Most babies  born with hearing impairments  have  sensori-neural  hearing losses.
These can be either congenital (genetically  inherited from the parents)  or due to
damage to the embryo in utero. Certain diseases such as  rubella (German measles)
or influenza that the mother contracts during pregnancy  can result in a sensori-
neural hearing loss as a birth defect in the child  (13).
What diseases can lead to sensori-neural hearing loss?

Diseases  such as  measles,  mumps,  scarlet  fever,  diphtheria,  whooping  cough,
influenza, and certain other viral infections  can lead  to sensori-neural hearing
loss.  The processes of these diseases can have a toxic effect on the sensitive
nerve  endings in the  crchlea.   Infections of  the cerebrospinal  fluid  such as
meningitis  can  also cause  damage to  the  cochlea.   Tumorous  growths  near the
auditory  nerve  can  cause  sensori-neural hearing  loss  due to  pressure  on the
nerve.  (13)
Can drugs lead to sensori-neural hearing loss?

High doses of ototoxic  drugs such as quinine,  dihydro-streptomycin, neomycin, and
kanamycin can have  toxic effects on  the cochlea  and cause subsequent sensori-
neural hearing loss (13).  The use of these drugs is now restricted.
Vhat is the extent of hearing loss anong the U.S. population?

Based on the audiometric results  in 1960-62 Public Health Survey,  it  is estimated
that approximately 19 aillion Americans or 13 percent of the U.S.  population have
hearing losses  that  can  be  described  as handicapping.   Criteria recommended by
the  National  Institute  of  Occupational  Safaty and Health (NIOSH)  (25  dB HL
averaged at 1000, 2000, and 3000 Hz)  as the  beginning point of handicap was used
                                         2-7

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 Co  derive  these estimates.  The population suffering such losses increases with
 age  and  the number of people significantly accelerates  after age 40.

 Information gathered by EPA and the National Association  of the Deaf show that
 13,362,842 Americans of all ages have some typo of hearing impairment, from mild
 to  severe.  One-half of these  people are  age  65  or  older.  There are 6,548,842
 Americans  of  all  ages  with significant  bilateral damage.   There are 1,767,046
 Americans of all ages that are  deaf.  Of these, 410,522 are prevocational (prior
 to  age 19) and  201,626 are  prelingual (prior  to  age  3).   The prelingual figure
 essentially represents  those who were born deaf.   Three  out  of every  100 school
 children have some type of hearing  impairment and 30 out of every 1000 Americans
 age  65 or  older have a hearing loss.    In  1971  the  U.S.  Public  Health  Service
 conducted a survey which  found that hearing impairment is  the  moat  frequently
 reported health  problem  in  the  country,  with  seven out of  avery  100  people
 reporting a hearing problem.   (19)
NOISE  INDUCED  HEARING LOSS

Vhat is Noise-Induced Permanent  Threshold  Shift  (NIPTS)?

NIPTS  is   a  permanent  shift  in  the  hearing  threshold  (a  lowering  of  the
sensitivity)  of  the ears due to exposure to noise.  It  is a sensori-neural type of
hearing loss,  and  is not  reversible  (14).   NIPTS  can  result  from  either  a
single exposure to  high  intensity  impulsive  noise  such  as  blasts  or  explosions,
or to  longer exposures  to  lower,  but  still damaging noise  levels.  Typically,
hearing loss  due   to  noise exposure  occurs  first at  the higher  frequencies,
particularly  around the  4000 Hz  level (3000 - 6000  H=) (13/54).  Figure 2-4 shows
an example of NIPTS relative to  exposure  levels  of 87-102  dB (17).
                                        2-8

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What  type  of  relationship exists between hearing loss and the  level  and duration
of noise exposure?

In general,  Che magnitude  of noise-induced hearing loss depends upon the noise
levels to which the ear has been habitually exposed,  the  length of time for which
it has been  exposed to those levels, and  the susceptibility  of  the  individual.
Short-term (time  in minutes) to high intensity noise, or  long-term  exposure  to
noise of lesser intensity, may  cause  temporary or  permanent hearing  loss.  With
an adequate time  before  the  next noise exposure, the  ear will generally recover
to a previous pre-exposura threshold.  Repeated  noise exposures without adequate
time  for  recovery  between  exposures can lead t;   a  Noise-Induced Permanent
Threshold Shift (NIPTS).  (See  References  18 and 20  for  a  general discussion.)
What  factors  can  increase  a person's  susceptibility  to noise-induced hearing
loss?

A significant factor  that  is known to increase Che likelihood of noise-induced
hearing loss is  continued  exposure to hazardous noise.  Defects or diseases  of
the ear ara hypothesized to cause a predisposition  to noise-induced hearing  loss
(14).  Some evidence exists  that  persons  are especially susceptible to suffering
                                         2-9

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 hearing  damage  from  noise  when  they  are  going  through  physiological change, or
 are  enduring physical  stress such as rapid growth or illness (20).
Does noise act svnergisticallv with drugs on hearing?  Are there other kinds of
synergistic effects?

There  is  some evidence in the literature  which  suggests  that ototoxic drugs such
as kanamycin, and a class of antibiotics  known  as aninoglycosides may cause more
severe damage to the ear when treatment with these drugs occurs concurrent with
noise exposure (21).  However, only little research has  been  done  in this area,
and the data are limited to animals.

Continuous noise  may also  interact  with impulse noise  and  body  vibrations to
exacerbate hearing  loss,  although  the magnitude of  this  effect is not  exactly
What factors protect the aar against noise-induced hearing loss?

There are several  factors which  can  mitigate  the risk of noise-induced hearing
loss.  The acoustic reflex (tightening of  the  oss?'cular  chain  due  to contraction
of  the  muscles in  the  middle ear  in response  to high  level  sound) protects
hearing  from  noise  exposure  to  a  very  limited degree.   The use  of hearing
protection such as earplugs  or eanauffs reduces  the risk of hearing damage  from
noise.   Avoidance of noisy areas, limiting exposure to short periods of time,  or
ensuring intermittent rather than continuous exposure will mitigate the risk  of
hearing loss from  noise.  Increased  public awareness  of the  dangers  of hearing
damage   from noise  can  lead  to the  use of ear protectors  and the avoidance  of
dangerous noise exposure.  (14)
                                       2-10

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What effect does sex have on the susceptibility to noise-induced hearing loss?

Based on the results of existing r3search,  it is not possible to  Conclude whether
the sex  of the noise-exposed person  increases  or  decreases the risk of noise-
induced hearing loss.
What is the  physiological basis  for noise-induced hearing loss?

The following mechanisms are considered  to play a role in causing damage to the
sensory cells of  the  inner ear:

    o     Destruction of  cochlear tissue b .ause of  the  physical  force of the
          sound pressure.,
    o     Cardiovascular  factors resulting  from diminished blood supply to the
          cochlea during noise exposure,
    o     Alteration  of fluid transport  across Reissner's aerabrane during noise
          exposure,
    o     Alteration  of biochemical processes during  noise exposure.
                                                                   (49)

The hair  cells  normally  convert  the mechanical  energy of sound  vibrations into
nevro-electrical  signals that are transmitted to the brain.   As  the intensity of
the  noise or  the time for  which the  ear  is exposed is  increased,  a greater
proportion of the hair cells are Jamaged or  destroyed. Figure  2-5 schematically
shows  the progressive  destruction of  the  hair  cells  due  to  excessive noise
exposure.
                                         2-11

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                                Teclonal Vembrint
                   « Fib«n
               (A) NORMAL ORGAN OF CORTI
                                                      3 Outer Hjir C«llj Absent
                                                          \\\
     Oinorrrd
     Pillif C*(l        Swollen
               Sopponing Cctls

   (B) PARTIAL INJURY
                       Colljpw of Organ of Com
                      Hair Cells Absent — Accruory
                       C*Mt Swollen i
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What is the "Equal Energy" hypothesis?

The "Equal Energy" hypothesis  is  another way to attempt to predict NIPTS.  The
hypothesis rtates that equal amounts of sound energy will cause equal amounts of
NIPTS regardless  of  the  distribution of the  energy .across   time  (18).    this
means that the  hazard  to hearing  is determined by  the total energy (product of
sound  level  and duration)  that  enters the  ear  on a daily basis.   The "Equal
Energy'1 rule allows  a 3  dB  increase  in  sound pressure level for each halving of
the duration of continuous  daily steady-state noise exposure (14 )•

In  determining  permissible  exposures for the workplace to  prevent  NIPTS,  OSHA
adopted a 5 dB  per doubling  rule  to  account  for  various breaks  in  noise levels
which occur during the day  (25).

EPA has identified an L   ,„.,. of 70 dB as the maximum 24-hour exposure necessary
to protect hearing.   If ex-osure time is reduced to 8 hours,  a maximum u   ,.., of
75 dB,  a 5 dB  increase,  has  been  identified  as a protective level for hearing
(5 ).
IMPULSE  NOISE
What is impulse noise and what are its effects on hearing?

This is noise characterized by a  short  duration, abrupt onset and decay and high
intensity.  Impulse noise describes the kinds of sound made by explosions, drop
forge  impacts, and  the  discharge of firearms.     Exposure  to  impulse  noise aay
result  in temporary and permanent shifts  in the threshold of hearing (22).

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What are the criteria for impulsive noise inside and aws• from the workplace?

OSKA regulations define impulse or impact  noise  as "sound with a rise time of not
more than 35 milliseconds to peak intensity and a duration of not more  than 500
milliseconds."  The  regulations  specify  that  employees shall not be  exposed to
impulse or impact noise which exceeds 140 dB peak pressure level.  (25)

The Committee on Hearing, Bioacoustics, and Sioir.echanics (CHA3A) of the  National
Academy of Sciences has also recommended  damage  risk criteria for  impulse noise.
The CHABA impulse curve is based  on  peak sound pressure level and the  duration of
the  impulses.   Figure  4-6 shows  the criteria  currently  in use,  assuming  an
exposure of 100 impulses per day.  The A-duration is the time that the impulse is
initially within 20 dB of the  peak level.  The B-duration measures the total time
that the sound is within 20 dB of the peak level.  The B-duration also  accounts
for any reflections  or  reverberation  that may be present,  and thus  allows less
exposure under these conditions.  A correction  factor  for daily exposures other
than 100 impulses is provided (74).
           165
           160
       UJ
       CE
       <
       UJ
       Q-
           15C
145
           140
           135
                              ^v^  A-DURAT1CN
                       1
                      0.1
                      I         I
                      1         10
                    DURATION - MSEC.
                                                   100
                                                           1000
                •IG. 2-6.   BASIC LIMITS FOR IMPULSE NOISE
                           EXPOSURE ASSUMING 100 IMPULSES
                           PER DAY AMD OTHER CONDITIONS  Ail
                           STATED III THE TEXT.
                           Source:  Ref. 74.
                                       2-14

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PRESBYCUSIS - SOCIOCUSIS
What is prasbycusis?

Presbycusis is a hearing loss associated with  increasing age.  It is most marked
at higher frequencies, especially those  above 3000 Hz.  The causes of presbycusis
are believed to be deterioration of  the  central nervous systea and changes in the
auditory system (12).
What is sociocusis?

Sociocusis   is   noise-induced   permanent   threshold   shift   (loss   of  hearing
sensitivil/)  attributed   to   environmental   noise   (hearing  loss   from  nor-
occupational noise exposure) (27).  It is difficult  to separate sociocusis  from
hearing  loss due  to  aging  (presbycusis)  or  to  occupational noise  exposure.
Exposures to high levels of environmental noise may  accelerate  loss normally due
to aging  (18).
What is the progression of presbycusis with age?

The threshold of hearing  rises  naturally  (hearing becomes  less  sensitive)  with
increasing age.   This effect involves primarily  the  frequencies  above 3000 Hz
(14).  Figure 2-7 presents data that depict the progression of presbycusis  with
age and the degree of loss.   As  age increases, louses at high frequencies become
greater and hearing  loss progresses further down the scale to lover frequencies.
                                        2-15

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             500      iooo      :aoo      3000      icoo      sooo
                       FREQUENCY  IN HERTZ
FIG. 2-7.  AVERAGE  HEARING LOSS FROM AGING  FOR >CN AND *OMEN  (WITHOUT
           THE  EFFECTS OF OCCUPATIONAL NOISE)
           Source:   Kef.  26
                                2-16

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Due  to  our complex, noisy  environment  it is difficult,  if  not impossible, to
separate hearing  loss  due to aging  from  noise-induced  hearing loss, both  from
occupational and environmental noise. Few people live their whole  lives  in quiet
surroundings.  Almost everyone suffers some exposure to damaging noise; either at
home, at work, at leisure, or during transportation between these activities.

The data found in Figure  2-7  are not meant to be taken as  an exact prediction of
the magnitude  of  hearing loss at each  age.   Different researchers  have found
differing  values.   The  figure  is  presented to represent  an  average amcjnt of
hearing  loss  that  can  be expected.  However,  it  is  possible  that some of  the
hearing loss described in the graph  is due to exposure to environmental noise and
not to presbycusis.   Some  researchers contend that  presbycusis  consists mainly of
hearing  loss  due  to lifetime exposure  to the  aggregate  of noise  found in the
environment.  Another view states that environmental  noise only accelerates the
losses  at   high  frequencies  that  would  have  occurred  anyway through aging.
(27)
What evidence exists that  sociocusis (hearing loss caused by environmental noise)
Rosen  conducted  a study of the  primitive  Mabaans  of the African Sudan.  Their
environment was almost free of noise with a typical  background level  of 40 dB (A-
weighted).  Among the Mafaaans,  the hearing abilities of men in  their seventies
and eighties is equal  to that of healthy children at age ten.   (28)

These  findings suggest that the  Mabaans show little if any hearing loss due to
aging  (presbycusis).   The  implication  of these findings  is  that  much of the
hearing  loss  observed with age  in  industrial  countries  could really be due to
environmental  noise  exposure  (sociocusis)  rather  than  aging  (presbycusis).
Rosen's  findings  may  be attributable to  diet  or other  causative  factors,  and
influenced by  difficulties  in determination of  age.
                                         2-17

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Is roc',-, music considered  Co  be  a hearing hazard?
Studies have confirmed that overall sound  levels of loud rock and roll, either  at
concerts or from domestic stereos, frequently  exceed  current hearing damage risk
criteria.    These  noise  levels  can  produce  large  amounts  cf  noise-induced
temporary  threshold  shifts  (MITTS)   in  both  the  musicians  and the  listeners.
Sound  levels in  the area  of  the band vary from 105-115 dB  and  in the dance area
from  100  to   110  dB  (A-weighted levels),  which  are within  hazardous  levels
according  to  damage  risk criteria established  by EPA, OSHA,  and NIOSH.   (29)
Attendance at a rock concert   as a fan, or  playing  and practicing in a rock band,
can  impair hearing  (30).   Figure  2-3  shows  before  and  after audiograms   of
musicians  and  diricers at  a  loud rock concert  (27).   NITTS  from  exposure  to the
loud music is clearly visible.  Generally, however, the incidence of hearing loss
is not  as  large  as  would  be  predicted (29).
One  factor  that  can  lessen  the  effects  of  rock  music  on  hearing  is  its
interrnittency.   Rock music is characterized  by on-times of  approximately three to
five  tinutes  alternating  with  off-times  of  approximately  one  minute   (27).
Another  factor is the prominence of low frequency soundjwhich are not as damaging
as high  frequency sounds.
    so
    TEENAGE B4NO
    "CUBES!  BATING
    ItOCX 8 ROLL "USIC
                        Ill <•» - 1 NOI.«»
                                                    TEENAOE  OANCERS EXPOSED TO
                                                      ROCK a ROLL MUSIC
                                                               III «i* - J MOUKl
                                                               II • 10
             IOOO   200O   3COO   »OOO   6OOO
               TEST  FPEOuEHCT   (MI)
                                           5OO    :OCC   2COO   200O   «OOO   6COO
                                                  TEST  FBEOUEMCT  I Mil
TIG. 2-3.  HEARING LEVELS  OF  TEEN-AGE ROCK-AND-ROLL  MUSICIANS AND
           DANCERS MEASURED JUST 3EFORE AND 3ET'.-rEEM  FIVE TO ELEVEN
           MINUTES AFTER A THREE-HOUR "ROCK SESSION" 'vITH AVERAGE
           SOU^JD  LEVELS OF 112 d3, A-VSIGHT2D.   DATA .ARE FROM ?HS
           SA.MPLE OBSERVATIONS.
           Source:   Ref.  27
                                    2-18-

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THE  CONSEQUENCES  OF HEARING LOSS

How  is  the ability  to discriminate and  understand  speech affected by  noise-
induced hearing loss?

Often, the first awareness of hearing loss comes with missing occasional words  in
general  conversation   and  having  difficulty  understanding  speech  on   the
telephone.   Many  sufferers of  noise-induced hearing  loss  say that speech  is
frequently garbled and distorted.  Typical noise-induced hearing  loss  is  in  the
high frequency range and persons with this type of hearing Ios3 can  have  normal
or  almost-normal  hearing up  to 1000 Hz.   They  exhibit  little  difficulty  in
hearing voices at normal intensities but they can have trouble understanding them
especially  with noise  in  the  background.   This  is   because  consonants  are
characterized  by  high  frequencies  and  weak   intensities  and vowels  by  low
frequencies.   A  person with a noise-induced  hearing  loss  can  miss hearing
r.onsonants  like  £, _f,  and  £  that givp  information  and meaning  to speech  and
language.  It is often difficult for people with this  type of loss  to understand
speech  in  lectures,  meetings,   parties,   theatres;  or  on  TV, radio,  or  the
telephone.
What is recruitment?

Recruitment  is  a  rapid increase in the perception  of  loudness  at  levels  above
hearing thresholds.  It is  often characteristic of a sensori-neural hearing loss
(13/48) and it may cause discomfort  an.' pain.  Once a sound  is intense enough for
the  subject   to  perceive  it,  an  additional  increase  in   intensity  causes  a
disproportionate  increase  in the sensation  of  loudness.  For  example,  a person
with a 40 dB  hearing  loss  would just  barely detect a sound of 40  dB  above the
normal threshold of hearing.  However, he would hear a sound of 50 dB above the
normal threshold with a Icudness that was  greater than that with which a noraal
hearing person  would hear  a- sound of  10 dB  above the threshold  of  hearing.
(13)
                                        2-19

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What is tinnitus and how nany people incur it?

Tinnitus  is  buzzing,  high pitched  ringing,  or roaring  in  the head  that  is a
common  complaint  of   person? with    hearing  loss,  particularly  those  losses
associated with noise.   Tinnitus  is often the  first  recognizable indicator of
hearing damage. It  can be in  one or both ears, alfhough there may not necessarily
be a hearing loss present.  (13)

According  to  the  National Health Examination  Survey  (1960) 32  percent  of  the
population or 48 million Americans have experienced some form of I'lnnitus, at one
time or another.
What other effects can hearing loss have?

Hearing loss can lead to  reduced employability of the sufferer.   It is especially
damaging  if  children suffer hearing   loss  during  their  developmental  and
educational  years  (32).    Hearing  loss   can  also be  a  safety  hazard and  can
contribute to accidents because warning  signals  or calls for help can-be  missed
by a person with a hearing loss (33).
What are the social consequences of hearing loss?

Many  times,   friends  and  associates  become  less  willing  to  be  partners  in
conversation or other activities with a person who  suffers  a  hearing loss.  It
becomes difficult for a  person  with a hearing loss  to participate  in lectures,
meetings, parties,  theatres, and other public gatherings;     to  listen  to  the TV  or
radio; or have telephone conversations.   A severe sense of isolation  can set in
as hearing decreases.  As hearing loss increases so does the sense  of being cut
off from the  rest of the world.   Eventually hearing raay decrease to the  point that
the person no longer  feels  a part of the living world.  Emotional depression can
be the result,  (12)
                                        2-20

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HEARING  LOSS  CRITERIA
What  level has  been identified  as  protective of  Che  hearing of  the  general
population in the workplace?

Taking into account  that 4000 Hz is the frequency  most sensitive to hearing loss
and  that  losses  of  less than  5  d3 are generally not considered  noticeable  or
significant, EPA has identified an 8-hour exposure level not exceeding 75  dB  in
order to protect  96 percent of the population frora  greater  than  a 5 dB NIPTS (5).
This recommendation  is  based  on  steady noise  levels  of  8  hours per  day,  5 days
per week, over a period of 40 years (5).
What  levels  have been  identified  as  protective of the hearing  of  the  general
population from  significant damage  due  to  environemtal  noise?

Environmental  noise  differs   from  workplace  noise  in  that  it xS  generally
intermittent, covers 365 days  per year rather than 250 work days, and covers 24
hours per day  rather  than  8  hours.   Taking these factors into account,  EPA has
identified an environmental noise level  of  L   ,., •. • 70 dB in order to protect 96
percent of the  general  population from a hearing loss of greater than  5 d3 at 4000
Hz (5).  For details, see Table 2-1.



Leq, 8 hour

Leg, 24 hour




250 day/year
365 day/year
250 day/year
3C5 day/year
Steady
(Continuous)
Noise
73
71.4
63
66.4

Intermittent
Noise
78
76.4
73
71.4
With
Margin of
Safety

75

70
         TABLE 2-1.  (AT-EAR) EXPOSURE LEVELS THAT PRODUCE NO
                     MORE THAN 5 dB MOISE-INDUCED HEARING DAMAGE
                     AT 4000 HZ OVER A 40-YSAR PERIOD
                     Source:  Ref. 5
                                        2-21

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If the assumptions  underlying  this identified level were changed, how would that
affect the level?

    o     "How would  the  identified  level  be  affected  by  a  change  in  the
          percentage of  the population protected?

          Reducing   the  96th  percentile  value  to  the  50th percentile  (i.e.,
          protecting half  the population) would  increase  the  protective  level
          value from 70  JB to  77  dB.

    o     "Since  agreement  on the  value of  the  intermittency correction  is
          imperfect,  what other values might be  used?

          The estimated  intermittency correction used  in the Levels Document is 5
          dB.  The  true  intermittency correction  is probably within  the  range 0
          to  15 dB.

    o     "Hov accurate  is the equal  energy assumption?

          The equal  energy assumption when applied to the long times  (8 hours to
          24, or 250 to 365 days)  is fairly accurate.  It may be suoject to  error
          when applied to short exposures of extreme  level.

    o     "How meaningful are  the basic studies  of hearing  damage risk?

          The probable errors  of  estimates in  the three basic  studies  cannot be
          stated  with absolute accuracy.   There are  a number  of problems  in
          extrapolating  percentages  of the population damaged  from  relatively
          high exposure   levels to  the protective  level.    Also,  there  is  the
          problem of  determining  the  amount  of hearing damage  when  the  control
          (non-exposed)  population is  subject to high levels of non-occupational
          noise.   Thus,   the 70 dB  protective  lavel is sinply  the best  present
          estimate,  subject to change if better  data  become  available."
                                       2-22

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            30-1
             25-
         03
         •o
         I   20-

         35
         o

         O

         
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What criterion has been developed for exposure to steady-state noise.

Figure 2-9 shows curves developed from data used in the  EPA Levels  Document (5)
which depict  the  maximum and average  noise-induced  permanent threshold  shift
expected averaged  over a 40-year exposure  to a 24-hour  continuous  A-weighted
equivalent scund level.  For  example, over a 40-year (age 20 to 60) exposure to a
continuous A-weighted equivalent sound  level of  75 dB, the average noise induced
permanent  threshold  shift  (NIPTS)  expected is  approximately  4 dB at  4000 Hz.
This means  that  at age 20,   the  individual will  have hearing  equal  to  the non-
exposed population (0  dB NITPS).  At age  60,  the individual will have  an NIPTS
considerably greater than 4 dB.   The average expected shift in  threshold is 4 dB.
This change  in  hearing is  caused by the workplace noise  exposure.   This 13  in
addition to the expected loss of hearing due to aging which at the age  of 60 is
approximately an average Loss of 24 dB for each frequency in the  range  of 250 -
8000 Hz  (26).   The maximum values indicated  in  Figure  2-9  show  the  worst case
expected from the given sound level.
HEARING CONSERVATION
In what ways can noise problems be approached in order to lessen the chances cf
hearing loss due to exposure to noise?

Attempts to solve a noise  problem  can  be made by attacking any combination of  the
three basic elements of the problem:
    o     By modifying the source to reduce its noi.se output
    o     By altering  the  transmission  path  to  reduce the noise level reaching
          the listener
    o     By  altering  the  receiver'3  exposure  either  through  limiting   the
          exposure time or by providing personal protective equipment    (11)
                                        2-24

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In what ways can a source be modified to reduce its noise output?

Noise sources can be quieted by:
    o     Reducing inpact or impulsive forces
    o     Reducing speed in machines, and flow velocities  and  pressures  in fluid
          systems
    o     Balancing rotating parts
    o     Reducing frictional resistance
    o     Isolating vibrating elements within  the machine
    o     Reducing noise radiating areas
    o     Applying vibration damping materials
    o     Reducing noise leakage from the interior of the machine
    o     Choosing quieter machinery when replacing appliances     (11)


In  what  ways can  the  transmission path be  altered to reduce  the noise level
reaching the listener?

Noi:ie transmission paths can be altered by:
    o     Separating the noise source and receiver as much as possible
    o     Using sound absorbing materials
    o     Using iound barriers or deflectors
    o     Using acoustical linings
    o     Using mufflers, silencers, or snu^'ers
    o     Using vibration isolators and flexible couplers
    o     Using enclosures    (11)
                                         2-25

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If it is impossible technologically or unfeasible economically to solve a noise
problem by modifying  che  source  or altering the  transmission  path,  what other
methods can be used to protect the listener from hearing damage?

Limiting the amount of continuous  exposure  to high noise levels is one approach.
This can bs  accomplished  either  by conducting noisy operations  for  only short
periods of  time or by allowing listeners  to be exposed to high levels of noise for
only short  periods of time.   After all other methods have failed to reduce noise
to acceptable levels, personal hearing protectors can  be used  as  a last  resort
where exposure to these high levels is required.  (11)  Hearing  protectors do
not solve the noise problem;  they  only  treat  the  symptoms of the  problem.
How is the exposure of workers to high levels of noise regulated by the Federal
government?

The Valsh-Healey Public Contracts Act of  1938  as  amended  in 1969 requires that
all companies doing at least  $10,000 annual business with Che Federal government
limit the exposure to noise at various levels of their workers to the durations
detailed in the table below.   Table 2-2 shows that as the noise  exposure  level
increases by 5 dB,  the allowable  tine  of  exposure  is  halved.   (25)

These  same  occupational exposure  levels  were  promulgated  covering industries
engaged   in   interstate  commerce  by  the  Occupational   Safety   and  Health
Admiristration (OSHA) under the mandate of the Occupational Safety and Health Act
of 1970.    In  November 1981,  OSHA adopted a hearing conservation amendment which
would  require  industries  with an L^    of 85 dB or greater to implement noise ex-
posure monitoring  and hearing conservation programs.  (99)
                                        2-26

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Duration Per Dav
(h)
8
6
4
3
t
1.5
1
1/2
1/4 or less
Noise
Slow
90
92
95
97
100
102
105
110
Level dB
Res pons e








115 max
                TABLE 2-2. PERMISSIBLE NOISE EXPOSURES UNDER THE
                           WALSH-HEALEY PUBLIC CONTRACTS ACT, 1969
                           Source:  Ref. 25

It noise exposure exceeds these limits what additional protective measures do the
OSHA regulations  require?

If  nois*  exposure  exceeds  these  duration  and  noise   level   limits,  after
economically  feasible engineering  remedies are exhausted,  employees are to wear
hearing protectors  issued by  the employer  (25).
What different  types of hearing  protectors are available?

Hearing protectors can either be earplugs or  muffs.  Earplugs can be made of many
materials,  such as soft  flexible  plastic,  wax,  paper,  glasswool,  cotton,  and
mixtures of these materials.  To be effective they must provide  a  snug,  airtight
and comfortable seal.   Muff-type  protectors  cover  the entire external  ear and
generally provide greater protection than do  earplugs.  (23)  Figure  2-10 depicts
the sound attenuation  characteristics  of  several  representative types of hearing
protectors.
                                         2-27

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                                  Wix-lmprfgnaied Sloppl«,
                                 Proptrly-Firted Plastic Inseru
                                         I
         100
                  200
                              500      1000      2000
                                Tf, Hi (In Cydn p«r Second)
                                                            5000
10.000
     FIG.  2-10.   SOUND ATTENUATION CHARACTERISTICS OF VARIOUS
                  TYPES OF  EAR PROTECTORS
                  Source:   Ref.  23
What other  requirenents rausc  ba fulfilled  under Che OSHA  Act  of 1970?
The Act requires  yearly audiograns for all employees whose noise exposure exceeds
the  OSHA  limits.    In  addition,  these  employees  are  to  be  issued  hearing
protection  devices.

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What are baseline and follow-up audiograms and why are they useful?

Baseline or reference audiograms  are the results of hearing tests performed on
new employees  at  their  time of hire.   Follow-up audiograms are periodic tests
performed to identify any deterioration in the employee's hearing due to on-the-
job noise  exposure.  Baseline  and  follow-up audiograms are  important because
employers  are only  liable for hearing  loss incurred  during  the time  that a
claimant  was   employed  by  them.   Baseline  audiograms  pinpoint the  extent of
hearing loss prior  to starting work  and also can serve as a  placement mechanism.
An effort can  be made to  place employees with an existing hearing loss in areas
that are  less  damaging  to their remaining hearing.  Follow-up 'audiograms point
out developing hearing loss problems and determine  those susceptible individuals
who  are at risk.   Their  exposures  should be modified  immediately  to protect
against continued  deterioration of hearing.   The follow-up periodic audiograms
help in pinpointing those individuals needing further testing and in documenting
compensation claims  (13).
Why is compensation  paid  for hearing  impairments?

In  recent  years  occupational   diseases  have become  corapensable,  and  loss of
hearing  has been  recognized  by the  Federal government and most  states  as an
occupational  disease.   Today,   there  are  some  state laws that consider gradual
hearing  impairment as a series  of traumas  or  accidents, and therefore ireat  it as
a safety rather than a health problem.  At  the present time nearly all  states  have
provisions  for compensating hearing  loss but  the  statutes vary  considerably.
While a  few states compensate fairly liberally,  some states  require "total"  loss
of hearing  in  one  or both ears, and others still require proof  of disability and
lost wages  (34).   (For general  information and discussion see Reference 38.)
                                        2-29

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In  terms  of  compensation  and  criteria,  how  are  disability,  impairment,—and
handicap defined and used?

    o     Disability:  actual or  presumed  inability  to remain employed at full
          wages

    o     Impairment:  a. deviation or a change  for  the  worse in either structure
          or function, usually outside of the range of normal

    o     Handicap:   the disadvantage  imposed by an  impairment  sufficient  to
          affect one's personal efficiency in the activities of daily living

Clearly,  the  term handicap  is  meant  to  apply to the compensation situation,
whereas the term impairment  is more appropriate to preventive criteria (35).  The
                    x
decision of what is an unacceptable amount of  impairment continues to be somewhat
in dispute.
What are :he two most often used hearing impairment compensation formulas?

1.  A.MA/AAOO Formula (1973)

This  recently  revised  formula  was   developed  by   the  American  Academy   of
Ophthalmology  and  Otolaryngology.   The  formula averages hearing  loss at 500,
1000, 2000, and 3000 Hz (prior to the  revision,  the 3  '£Az  test  frequency was  not
used) with a 25 dB low fence below which no hearing impairment  is considered to
exist.  An average hearing impairment of 92 d3  is considered total hearing loss
with each decibel loss  between 25 and  92 dB representing a 1.5 percent  impairment
rate of growth (36).
                                         2-30

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2.   Compensation Formula for Federal Employees  (NIOSH Formula)

The original AMA (AAOO)  formula was used until 1969.  I!: was modified at that  time
by the Department of Labor to include test frequencies  of 1, 2, and 4 KHz with  the
same high and>low fence as before.  It was again modified  in  1973 to the present
form.  This later modification was largely based on NIOSH recommendations  in  its
criteria document, "Criteria for a Recommended Standard Occupational Exposure to
Noise"  (37).  NIOSH  recommended  that  hearing impairment   should   be assessed
by the-ability  to hear and understand speech not only  in quiet  surroundings,  but
in everyday conversational  settings where  significant background  noise  may  be
present.   The NIOSH formula averages  hearing loss  at 1000,  2000,  and 3000  Hz,
also using  a  25  dB  low  fence below  which no hearing  loss  is  considered.   A  1.5
percent hearing  impairment rate of growth occurs for  every decibel  loss above 25
dB.  The inclusion of the 3 KHz test  frequency while deleting the 500 Hz makes  the
                 _i
formula  more sensitive  to  noise-induced  hearing loss  since  such losses   are
incurred initially  at higher  frequencies.   In view  of this,  a number of  states
have incorporated similar high  frequency components in their  formulas in  recent
years.
                                         2-31

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NONAUDITORY PHYSIOLOGICAL RESPONSE
EFFECTS - GENERAL
 Why is  noise  considered a health problem?

 Noise  is  generally  viewed  as  being  one  of  a number  of general  biological
 stressors.   IE is felt that excessive exposure  to  noise  might be considered a
 health  risk  in that  noise  may  contribute to  the development and aggravation of
 stress  related conditions such  as  high  blood pressure, coronary disease, ulcers,
 colitis,  and  migraine headaches (20)*.

 Growing  evidence suggests  a link  between  noise and  cardiovascular  problems.
 There is  also evidence suggesting that  noise may be  related  to birth defects and
 low birth-weight babies (40).

 There are  also some  indications that noise exposure can increase susceptibility
 to  viral  infection and toxic substances  (14).
What physiological changes occur in response to noise?

Loud sounds can cause an arousal  response  in which a series of reactions  occur in
the  body.   Adrenalin  is  released  into  the  bloodstream;  heart  rate,  blood
pressure,  and  respiration  tend  to  increase;   gastrointestinal  motility  is
inhibited;  peripheral  blood  vessels  constrict;  and  muscles  tense.    On  the
conscious  level we are  alerted  and prepared  to take action.  Even  though noise
may have no relationship to danger, the body will  respond  automatically  to noise
as a warning signal.  (14)
 *References  are  listed in Section 11, e.g.:  (Ref. 20).
                                         3-1

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Illustrated  in  Figure  3-1  are  possible  clinical  manifestations  of  stress
concomitant with noise.  Not  only might there be  harmful consequences  to  health
during  the state of alertness,  but  research also suggests effects nay  occur when
the body is unaware or  asleep.
 SUMMARY OF POSSIBLE
 CLINICAL
 MANIFESTATIONS
 OF STRESS
 CONCOMITANT
 WITH NOISE
        GALVANIC
        SKIN RESPONSE
   INCREASED ACTIVITY
   RELATED TO
   ULCER FORMATION
CHANGES IN
INTESTINAL MOTILITY
                CHANGES IN SKELETAL
                MUSCLE TENSION
                                                  SUBJECTIVE RESPONSE
                                                  IRRITABILITY
                                                  PERCEPTION OF LOUDNESS
                                                     INCREASED SUGAR.
                                                     CHOLESTERAL. AMD
                                                     ADRENALINE
                                                       CHANGES IN
                                                       HEART RATE
                                                         INCREASED
                                                         3LOOu PRESSURE
                                                            INCREASED
                                                            ADRENAL HORMONES
                                                            (CORTICOSTERONE.
                                                            COHTISOL)
                                                         VASOCONSTRICT10N
                                FIG. 3-1
How  are  these physiological  responses activated?

Impulses  from the  brain activate centers  of the autonomic  nervous system  which
trigger  a  series  of  bodily  reactions  as part  of  a  general  stress response.
Systems   that   may   be   affected    include   th^   glandular,   cardiovascular,
gastrointestinal, and otusculoskelatal systems.

Is short-term exposure  to  noise  considered a health  risk?

No.  It is generally believed that there is no risk since the body has  a chance to
recover.  A  little stress, as many  people  will attest, may be beneficial.   There
may  be exceptions to the above  statement.   (41)
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Is Long-term exposure to noise considered a health risk?

It is possible  Chat  repeated  or  constant  exposure to noise can contribute  to  a
deterioration in  health.   Whether or not  environmental  or industrial noise by
itself can lead to chronic disturbances is hard to determine since there are so
many  other  stresses to  which  people  are  exposed   (41).    This research is
difficult  to  conduct and  little  has  been done  in  this area,  but  research is
accumulating which suggests a relationship between long-term noise exposure and
stress-related health effects, particularly those related to the cardiovascular
system.
Have criteria been established for the nonauditory effects of noise?

Not at the present time.  In the past,  EPA stated that noise levels identified to
protect  against hearing  loss  should be  sufficient  to  protect  against  the
nonauditory  effects  of noise.   However, growing  evidence suggests  that • this
assumption needs to be tested through research.  (5)  In considering noise as a
general  stressor,  the  need to establish  quantitative  criteria has  now become
evident, given the growing concern about  these effects.
 NOISE AND THE BODY'S  REACTIONS
Why is the investigation of cardiovascular effects so important?

The extent to which noise may contribute  to  the  prevalence of hypertension and
other  cardiovascular  disorders  points  to  an important public  health concern.
Heart disease has been the leading cause of  death  in  the  United States for the
past  several  decades,  accounting '.or  almost 50  percent of  the  deaths in this
country.  Hypertension is  the mosr common of  all cardiovascular diseases, and it
                                        3-3

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is estimated that from 23 to 60 million Americans, depending on the  criteria used
for  defining  hypertension and  the  age  groups included,  have  hypertension.
Hypertension is a factor contributing to the death of  at  least  250,000 Americans
each  year.  (84)  Heart and blood  vessel diseases  cause a  great  share of  the
financial burden  of  illness,  constituting about one-fifth of the  total cost of
illness in this country.
Is there  credible  scientific evidence which suggests that noise-induced stress
is related to hypertension and cardiovascular disease?

Yes.   It  has  long  been known  that  noise  is  capable  of  producing  short  term
systemic stress reactions in animals and humans.  The major question concerns the
extent to which  these  reactions,  if repeatedly elicited, translate into health
problems. Over  40,  mostly  foreign,  retrospective  epidemiological studies  have
been done assessing the  cardiovascular  effects of occupational noise.   (100,86)
A large number of these  studies indicate  that  long-term  exposure  to high levels
of occupational noise  is associated with  increased rates  of high  blood  pressure
and other cardiovascular health problems. Field studies have also  been conducted
on various  other groups  -  people  living  near  airports, and  school   children
exposed to traffic noise - showing  that  there may be some  risk for these people
(66,85).   In  addition, laboratory  studies on  animals   and  humans  (42)  have
demonstrated a relationship  between noise and high blood  pressure. It should be
noted that in field studies, while noise  may be the major  variable between test
and  control  groups, noise  cannot be singled  out  as the  only  cause  of stress
effects.  Attention has to  be paid to  the type of work being done,  other noxious
environmental conditions, and the physical and  emotional  health of the subjects.
(43)
Ara  there  any  studies  which  have  focused  on health  effects  associated with
community or environmental noise exposures?

Several correlational field studies  have examined health outcomes  as  a  function
of  exposure  to varying  levels  of  traffic and  aircraft  noise.   (66)   Although
                                  3-4

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these studies must be viewed  as  exploratory  rather than confirmatory, evidence
has  been obtained  for  increased  rates   of  hypertension  and  cardiovascular
disease,  increased  usage  of various  prescription  drugs,  increased  rates of
physician's  visits,  and  increased  subjective  and self-reported  symptoms and
complaints.  (86,101)  These studies  suggest  the possibility  of  adverse health
outcomes associated  wirh environmental  noise and further underscore the need for
additional research.
Is noise of special ecncern for  those  persons already suffering from circulatory
and heart problems?

Noise may be potentially mora  dangerous  to these people since it can aggravate an
existing health  problem.   There  are  millions with  heart disease,  high blood
pressure,  and  emotional illness  who  may need  protection, from  the  additional
stress of noise.  However.no research exists to document this area of concern.
Are children more susceptible to the physiological stress effects of noise?

The contribution of  various  environmental factors to  the  early development of
high blood pressure  is  an  important  question.   With respect to noise, at  least
two studies exist which  suggest that exposure to  high  noise  levels  in schools and
neighborhoods  is  associated  with elevations  in  blood pressure.    The  blood
pressure levels of children living in high  noise  environments  were found  to be
significally higher  than  those  of children attending schools or  residing in
quieter areas.   (96,100,104)
What  are  some  of the  findings  from the study of  blood  pressure in  laboratory
animals exposed to noise?

Research in this area has been sponsored by EPA.   Data from an experiment  by Dr.
Ernest Peterson, using  monkeys  subjected  to  24  hours of  recorded  noise daily
(reprtsenting  typical  daily noises  for an industrial worker),  indicate  that
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such exposures, repeated daily  for months, can  cause  sustained  changes  in  blood
pressure.   This  suggests that  noise  may  make  a  long-term contribution to  the
development of cardiovascular disease.  (42).
Have  any  long-term human  experimental or  other such  controlled  studies been
conducted?

One  long-term  laboratory  study has been conducted by the Navy.  In  this  study,
subjects were  exposed  to short  bursts  of noise at moderate  levels over a  30-day
period.  (102)  Among  the  results  found  in  this   study  were  statistically
significant elevations in cholesterol and cortisol.   Cholesterol  is a known risk
factor  for  cardiovascular  disease and cortiso! is a stress hormone.  Two other
field studies have been able  to  obtain high and low noise comparisons  on the same
subjects in field settings.  (103,86)  These studies  have reported noise-related
elevations  in  blood pressure and  in  various  stress-related hormones,  and have
found increases  in  a variety of health  disorders  and complaints.
        *                                                                  .
Is  there  a  relationship  between  noise-induced  hearing  loss  and  high blood
Studies have been  done which  have  tried  to  use  noise-induced hearing  loss  as  an
indirect  index of  noise  exposure.   Ono   such  study did  report  higher  blood
pressure  levels among workers with obvious noise-induced hearing loss.  However,
this study has been  criticized  on  methodological  grounds  and subsequent  studies
have yielded mixed  results.   (43,105)
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With what other stress effects can noise be associated?

Stress  can  be  manifested   in   any   number   of  ways,   including  headaches,
irritability,  insomnia,  digestive  disorders,  and  psychological  disorders.
Workers who are exposed  to excessive  noise frequently complain that noise just
makes them tired.

Quite a  few  field studies have  been  done on workers  ir  Europe,  examining the
relationship between noise and illness.  In these studies,  noise has been related
to the following:

    General morbidity (illness)
    Neuropsychical disturbances
          o  headaches
          o  fatigue
          o  insomnia
          o  irritability
          o  neuroticism
    Cardiovascular system disturbances
          o  hypertension
          o  hypotension
          o  cardiac disease
    Digestive disorders
          o  ulcers
          o  colitis
    Endocrine and biochemical disorders

There is  a need  for additional  laboratory  replications  of  these potentially
important findings.
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Do experts  agree  on the significance  of  nonauditory  physiological effects of
noise?
No.  Whil-> a growing body of evidence, provided and  accepted by a growing number
of  scientists,  suggests  that  noise  can  be  considered  a general  biological
stressor, not all  findings  and  not  all  scientists agree.   Dr. Karl Kryter (98,
20)  performed  studies  in  which  his  subjects  demonstrated  relatively  small-
physiological changes in response to noise.   He feels that the acoustic-vascular
response to noise can be explained by a nonstressful protective auditory system
sympathetic  nervous  system reflex  rather  than the  general stress  response
generally  assumed   to  be responsible  for  what he  believes   to  be  transient
physiological changes observed after noise exposure.  So there  are differences in
scientific opinion about both the mechanism by which noise affects  the body and
the degree to which these effects are stressful.  Many of these differences may
eventually be explained  in  terms  of the  distinct  ways in-which two  different
individuals may respond to an identical stimulus.
Have  increased illness,  accidents,  and absenteeism been related to noise?

A  study was  conducted on the medical attendance and accident  files of 500 workers
situated  in  noisy plants  (95 dB or  higher)  and 500 workers in quieter plants (80
dB or  less)  in the southeast U.S.  Comparing the records of those workers, it was
found  that  the workers  exposed to the  higher  levels of noise had a significantly
greater   rate  of  accidents,   diagnosed   medical   problems,   and  absenteeism
(especially  in the  boiler manufacturing plant  where most  of  the  records  were
obtained) (86).  The  study cautions, however, that there may be other conditions
besides noise responsible  for these differences.
 Does  noise have any nonauditory synergistie effects with toxic substances?

 There are  now 13,000 toxins used in industry and business.  Noise as  a stressor in
 combination with toxins may pose a serious health hazard for workers.  However,
 no  definitive  data  are available.
                                        3-8

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Does noise have an effect on mortality rates?

Some research has been conducted by W. C. Meecham and W. Shaw on the effects  of
jet noise and mortality rates around Los  Angeles  Airpoit.   Tne results  showed  an
effect that is provocative and suggest the need for more in-depth,  larger  scale
research.  Considerable caution should be  exercised in generalizing from  these
findings  since  there  were  many  intervening  noise  exposure   and  demographic
variables not  considered  in this  ecological-correlation scudy.   Therefore the
effects of noise on mortality are  still uncertain.  (97, 44)
Does protecting against hearing loss  guarantee  that no nonauditory physiological
effects will occur?

It is not possible to provide a definitive answer to  this  question at  this  time.
However, EPA-sponsored primate research  has  shown that significant and sustained
elevations  in  blood  pressure can be produced  as a  result of exposure to  noise
levels  which  do  not  produce  any  significant  permanent  hearing  loss  in  the
subjects.   (106)  These data would suggest that  protecting against the auditory
effects of  noise  dees  not  necessarily  prevent  the nonauditory  effects.    Human
data confirming this conclusion are needed.
Is there a  link,  between    annoyance and nonauditory  physiological response  to
Although it is reasonable to view  annoyance as a symptom or sign  of noise-induced
stress, no direst test of this relationship has been made,.
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NOISE  AND  THE  UNBORN
Can noise affect  the  fetus?

Physiologically,  there  are reasons to suspect that noise may affect  the  fetus.
Studies  have shovn  maternal stress  causes  constriction of  the  uterine blood
vessels  which  supply nutrients  and oxygen to  the  developing baby.    Stress may
then  threaten  fetal  development  if  it  occurs  early  in pregnancy.   The most
important  period  is about 14 to 60 days after  conception.   During  this time,
important developments  in  the central nervous system and vital organs  are  taking
place.   (45)  However,  it  is presently not known whether noise affects the fetus
in any       lasting ways.

As an example of  possible  outcomes due to fetal noise exposure, a Japanese study
showed  a statistical tendency  toward  low birth weights in noisy areas  near  a
major airport compared to surrounding areas (40).  Other intervening  factors that
may  have contributed  to  this  finding  such  as  maternal  stress  have not been
confirmed
         #

The    U.S.  study in  Los Angeles  found that.in  addition to  greater  incidence of
low birth weights,  there vas also  a greater  incidence of birth defects such as
clefts of the lip or  palate, and  spinal malformations.  These results should be
judged cautiously because  of the  many correlational problems with the data.

On the other hand, a  similar study  on fetal birth weight was       conducted by
the  Center  for Disease  Control  (85).    This study  found  that  there  were  no
effects  (46).
                                        3-10

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COMMUNICATION  INTERFERENCE
EFFECTS

The indirect effects  of  speech  interference  are;

    o     Disturbance of normal  domestic or  educational  activities
    o     Creation of an undesirable  living  environment
    o     Safety hazards
    o     A source of extreme annoyance      (i>)*
Can high background noise  levels  affect  social  interaction?
                                                            i
For certain individuals who live in noisy areas,  the adoption of a lifestyle that
is nearly devoid of communicition and social  interaction  can result.   If noise
interferes with their communication, they  stop  talking,  change the content  of
their conversations,  talk  only  when  absolutely  necessary,  and frequently  repeat
themselves (31).
How is communication interference  important  in  safety?

Masking of  warning signals  and directions  by other  intrusive  sounds can  be
hazardous.  For example,  an airlire  pilot's  reception of  an  air  traffic control
message can  be  affected by too much background noise.  A  missed warning in a noisy
steel mill can result  in  an accident,  injury, or  even death  (47).
* References are listed in Section 11,  e.g.:   (Ref.  5).
                                        4-1

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Can vigilance be disrupted by noise?

Yes, listening  for particular signals can  be  hindered  by  high  background noise
levels,  For c.;-vnpls, a parent working downstairs might  be  listening  for sounds
of a child  upstairs  awakening from sleep.  A noisy  environment  could  interfere
with this.

What factors determine "he extent  to which  noise affects  speech  communication''

     o    Location (whether  indoors or outdoors).

     o    The   attenuation  characteristics  of   the   building  and   internal
          structures wheu  indoors.

     o    The vocal  effort and skill of  the talkers  and  listeners.

     o    The background noise level and  spectrum   (5).

     o    Hearing  acuity.

Does speech qualify  have an  effect on speech  interference?

If the talker is imprecise in his speech  (poor articulation),  speaks a  different
dialect  than  the listener,  or speaks  softer than  most,  lower background  noise
levels are required  (14).

Is the duration  of the noise a determinant  in speech interference?

Intermittent  noises  will mask speech  in variable  degrees.   Impulse noise  in
isolated one-second  bursts is unlikely to disrupt much  speech communication  jue
to the redundancy of  speech.  However, as the frequency  and duration  of the  noise
bursts increase, so  does the masking effect  (14).
                                     4-2

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Do fluctuating sound levels have any effect on intelligibility?

For a  fixed  L  ,  sufficient to mask  some  speech,  interference  with speech  is
              eq
greater for a steady noise  than for almost all types of environmental noise whose
magnitude varies with tiaie (fluctuating sound levels)  (5).

What methods  are used  to characterize  noises  in respect to  their  speech-making
abilities?

     o    The Articulation Index (AI), a complex measure which accounts  for  the
          differences  in   masking  capabilities  of  frequencies   in  background
          noise.  (91).
     o    The  Speech  Interference  t.avel  (SIL),  an arithmetic  average  of  the
          octave-band  sound  pressure  levels  of  noise  that  affect  the  major
          speech frequencies (octave band sound pressure  levels  are  centered at
          500, 1000, 2000, and 4000 Hz).  (92).

     o    A-weighted sound level, which reflects  the  sensitivity pattern of the
          ear's response to noise and speech.  (14)

Why is the A-veighted  sound level a good measure of speech \nterferenee potential
of noise?

A-weighting gives the greatest weight to those components of noise that  fall in
the  frequency range  where most  speech information  resides.     It  gives  lass
emphasis to noise in  the  lower  frequency  (500 Hz or  low
-------
What are  the  appropriate  noise levels Co prevenr speech interference with oral
communication?

For  outdoors,  Table  4-1   shows  distance!   between  speaker  and  listener   for
satisfactory  outdoor  speech  at two levels of vocal effort in steady background
noise levels.  In other words,  if the  noise  levels in Table  4-1 are  exceeded,  the
speaker  and  listener  must  either   move  closer  together  or   expect  reduced
intelligibility.  This  is  also  shown  in Figure 4-1.
VOICE LEVEL *

Normal Voice ( in dB)
Raised Voice ( in dB)
COMMUNICATION DISTANCE (meters)
0.5
72
78
1
66
72
2
60
66
3
56
62
4
54
60
5
52
58
          TABLE  4-1.   STEADY  A-WEIGHTED  SOUND  LEVELS  THAT ALLOW
                      COMMUNICATION  WITH 95  PERCENT SENTENCE
                      INTELLIGIBILITY  OVER VARIOUS DISTANCES
                      OUTDOORS  FOR DIFFERENT VOICE LEVELS
                      SOURCE:   Ref.  5.
                      *ASSUMES  NORMAL  VOICE  LEVEL OF  70  dB
                      (67  dBA)  OR RAISED VOICE OF 76  dB  (73 dBA)

What criteria are  used  to  predict the effect  of noise on speech  communication?

For indoors, Figure  4-1 shows  that  an L,  of 50 dB  pennies  virtually 100  percent
intelligibility  within  buildings  (5).    (A  given   percentage  of  sentence
intelligibility, such as  95  percent or  100  percent,  indicates  the  proportion  of
key words in a group of  sentences  which are correctly heard by normal-hearing
listeners .)
For outdoors, Figure 4-2  shows  that  an  L,   of  50  dB  which  also  indicates  nearly
100 percent  intelligibility  (5).
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Figure 4-3 shows appropriate voice  levels  limited by ambient noise conditions.
Along the abscissa are various measures  of  noise, along the ordinate distance,
and the  parameters are  voice  level.  At levels  above  50 dB people raise  their
voice level as  shown  by the "expected" line if communications are not vital  or by
the "communicating" line if communications  are vital.  Below and to the left of
the "normal" voice  line  communications  are  at  an AI level  of  0.5,  98 percent
sentence intelligibility.   At  a shout,  communications are possible except  above
and to the right of the  "impossible" area line.   (50)
      100
                                                         I
                                            65          70           75
                    LEVEL OF CONTINUOUS NOISE CAUSING INTERFERENCE (dB)
         FIG. i-l.   CRITERIA FOR INDOOR SPT.ECH INTERFERENCE (RELAXES
                    CONSERVATION AT GREATER THAN 1 METER SEPARATION,
                    <*5 d3 BACKGROUND IN THE ABSENCE OF INTERFERING
                    NOISE)    SOURCE:  Ret. 5

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100
                    CONTINUOUS OUTDOOR NOISE CAUSING
                       INTERFERENCE (L  ), dB
        FIG. 4-2.  CRITERIA FOR OUTDOOR SPEECH INTER-
                   FERENCE (NORMAL VOICE AT 2 METERS)
                   SOURCE:  Ref. 5
                              4-6

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                                                   XV* DISTANCE NOISE
                                                       AREA WHERE UNAIDED
                                                       FACE-TO-FACE
                                                       COMMUNICATIONS
                                                       ARE INADEQUATE
        DISTANCE NOISE AREA
        WHERE FACE-TO-FACE
        COMMUNICATION IN
        NORMAL VOICE IS
        ADEQUATE
                            50       60        70
                          A WEIGHTED SOUND  LEVEL
100
                 FIG.  4-3,   NECESSARY VOICE LEVELS AS LIMITED BY AMBIENT

                            NOISE  FOR SELECTED DISTANCES BETWEEN TALKER

                            AND  LISTENER FOR SATISFACTORY FACE-TO-FACE

                            COMMUNICATION.

                            SOURCE:   Ref.  50,  28
NOTE:  The figures are based on data from "sentences known to listeners".  As a

result, these levels  may  not  be completely adequate  in  describing fluctuating

noise  conditions  and  would  be conservative estimates   for situations  where

communication is unpredictable.
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SPECIAL  POPULATIONS
Does  the age of adults have  any   ffeet  on  the  ability  to discriminate speech in
noise?

The  ability  to  understand  partially  masked  or  distorted  speech  begins  to
deteriorate  around  age  30  and  declines  steadily  thereafter.    Generally,
therefore,  the older the listener,  the lower  the  background noise must be for
normal communication.   (14)
Do  people with  hearing loss have  any special problems  with  regard  to speech
interference?

People with hearing losses require more favorable  speech-to-noise  ratios  than do
persons  with  normal  hearing (14).   This  means  that the difference between the
level  of  speech and  the  background noise  level must  be  greater  for  hearing
impaired  individuals  than  for  people with normal  hearing.   This can be achieved
either by decreasing  the background  noisr; level or  increasing  the speech level.
Increased levels of noise, in relation to  the speech signal,  tend to aggravate
the  adverse effects  of hearing  loss.   (48)
What  are  the  effects  of  noise  on  children's  communication  skills?

High  levels  of  noise reduce  the  number  of conversations  and  their  content,
quality,  snd  fidelity.   Children have a relative lack of  knowledge of  language
that  makes them  less able  to "hear1' speech  when  some of  the  cues  are  lost.
Repeated  exposure  to  high levels of noise in "critical  periods  of development'1
might affect  conceptual development and the acquisition of  speech,  language,  and
language-related skills  like  reading  and  listening.   (32)
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Can reading ability be affected bv high noise levels?

A study based on  the  reading  scores  of children in grades two through  five  who
live in an apartment  building  showed  that  the noise in and around  the  building
was detrimental to their reading development.  The  longer  the  children had  lived
in the noisy environment, the lower their reading test scores.  (66)
Are these effects only important at home?

Studies have shown  that  schools located next  to  expressways  or under aircraft
flight paihs also show severe effects  on learning.   For example in addition to
the length of the disruptive aircraft  flyovers, in many cases, considerable time
is spent refocusing  the students'  attention on the study material (32),
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PERFORMANCE INTERFERENCE


DETERMINANTS  OF INTERFERENCE


What noise parameters affect work performance?

The question is a complex one and in any particular case,  at least four factors
should be kept in mind:

    o     Characteristics of the noise
    o     Characteristics of the task
    o     Aspects of performance considered important
    o     Individual differences

In general, noise is more likely to reduce the accuracy rather than  the  total
tity of work   and it affects complex  tasks more than  simpler  ones  (,31).*   As
the noise level  increases,  both reaction times  and numbers of errors increase.
                                            j
These effects are more pronounced for complex tasks than for simpler tasks.   In
fact, for some simple Casks, noise may enhance performance.
How does noise exposure interfere with human performance?

Noise often results  in a disruption of  one's  attentional  processes.  Cues  that
are  irrelevant  to  task  performance are  dropped  out  first.   If  attention  is
further restricted, then cues that are  relevant  to  performance of  thu  task  are
eliminated.   (96)

Why does performance sometimes  improve during exposure to  noise?

Performance improves during exposure to noise when distracting cues are dropped
ouc.  Task performance improves  when only relevant primary task cues are focused
upon.  (96)
* References are listed in Section 15, e.g.:  (Ref. 31).
                                         5-1

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Noise levels most likely to be detrimental Co performance are;

    o     Continuous noise levels above 90 dB (A-weighted)
    o     Levels less Chan  90  dB (A-weighted) if they have  predominantly high
          frequency components, are intermittent, unexpected, or uncontrollable
                                                                        (5)

Does th° interaittency or predictability of the noise play a  role in performance
interference?

Yes, when  a noise occurs  in  a random,  intermittent or  unpredictable fashion,
errors  tend   to   increase,   and  greater  effort  is   required   to  maintain
concentration.  Unpredictable noise may lead  to breaks in concentration that are
followed by compensating increases in the work rate.  Thus,  the overall rate of
work may not be affected, but the variability of  the work rate may be. (51, 53).
Do high-intensity noises have any special effects on performance?

High-intensity noise such as jet engine noise in close proximity ia reported to
cause nausea,  vertigo,  uncoordination, fatigue, and  mental confusion.   These
effects  are  attributed  to vestibular  stimulation  and to  reflexes  elicited by
vibration of the skin, muscles,  and joints.  Any of these symptoms can give rise
to a reduction in performance efficiency.  (52)

Does controllability of  the noise have an effect on performance?

Noises that are unpredictable or randomly intermittent tend to be associated with
greater decrements in perfomance than in continuous  noise.  These decrements may
in  part  be  explained  by the  fact   that  these noises  are  perceived  by  the
individual as being unpredictable.

Recent research (56) suggests  that exposure  to unpredictable noise may result in
performance decrements which occur after the noise has ceased (after effects).

Does  the  frequency  spectrum of  the noise have any effect on performance?

Yes,  in  general,  high frequency noises (above  2000 Hz) impair performance more
than  lew  frequencies of the same sound pressure level

                                         5-2

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Does the meaning of the noise affect its ability to interfere with performance?

Yes, the meaning of the noise is an importart variable.  Relevant and meaningful
information is attended to, rather than ignored, thereby detracting  from the task
at hand.
What types of  tasks can be affected by noise?

    o     Tasks  that  involve concentration,  learning, or analytic processes
    o     Tasks  where  an  integral   part  of  performance  is  speaking  and/or
          listening
    o     Tasks  requiring fine muscular movements
    o     Simultaneous tasks
    o     Tasks  which require continuous performance
    o     Tasks  including prolonged vigilance and  few signals
    o     Performance of any task  that involves auditory signals
    o     Tasks  requiring attention to multiple channels          (20)

How can noise  affect  learning or information gathering?

Noise may compete  for the  limited  number of channels available  for information
input.  When the system is  already  overloaded, the individual must take more time
to evaluate the  intruding stimulus, or risk making errors (55).
Do  individuals  differ  in  the extent  to  which noise may  interfere with  their
performance?

Yec,  laboratory  studies have  shown  that  some  people who  have been exposed  to
noise are not able to perform  tasks  requiring  skills of  retention  and  attention
to detail.  These decrements in performance  are especially  found in those who  are
exposed to uncontrollable or unpredictable  noise  (56).
                                         5-3

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Research has  shown  that the motivational involven.ent of  the individual influences
the extent that noise will have   on  performance   (57).       Other studies have
shown  that  personality   variables,   primarily   the   trait  of  introversion/
extroversion,  can  influence performance  under noise  (58;  59;  60).
Can noise have cumulative effects on performance?

It has been hypothesized that exposure to noise can produce an actual change in
the state of the  individual that is reflected in failure of selective perception.
This  change  produces  measurable  performance  decrements  (14).    More  errors
tend  to  occur toward  the  end of  performance  sessions,  which also  suggests a
cumulative effect by the end  of the workday (61).
Can noise have both positive and negative effects on task performance?

Yes, depending  on  the  complexity of  the  task,  noise may  either  improve  or
interfere with performance.   Tasks that are mechanical or repetitive, and where
average levels of performance are  sufficient, will seldom be affected.  Moderate
levels  of noise can produce  beneficial arousal  levels  during  monotonous tasks.
Tasks  requiring moderate meffort  seem  to be unaffected by the noise.    Hizhly
co-jplex tasks requiring attendance to a large number of  cues, or to many cues in
rapid  succession,  may be   affected  by  noise  at   all  levels  of  intensity.
(62)
Does noise produce any after effects on performance?

Yes, research  has shown  that  noise may  produce  adverse performance  on tasks
performed after the noise is no  longer  present.   These effects sometimes occur
even when performance during noise was  not affected.   Aftereffects  aPPear
likely to occur when the noise  has been unpredictable or uncontrollable.  (56)
                                        5-4

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Is industrial noise considered a  problem  in  performance  interference?

Yes,  industrial noise  may  have  the  most  pronounced   effects  on  performance
including exhaustion,  absentmindedness,  mental strain,  absenteeism,  tenseness,
and irritability.  All of  these  factors affect worker efficiency.    (63)   It  is
reasonable  to  suppose  that  increased  absenteeism  can  come  from  workers'
psychological  aversion  to returning  each day to  an  unpleasant, noisy working
environment.  The frequency and severity of industrial injuries could tend to  be
higher  in  noisy  environments  because of  masking of  warning  signals  and  of
increases in momentary gaps or errors  in  performance  (64 ) •
What  is  the  estimated cost to society of  the  workplace  effects  of  noise  due  to
absenteeism, noise-induced  industrial  injuries,  and  performance  interferences?

    o     One day  per year, worker  exposed to  greater  than  85  dB
    o     About  $250  per  worker  per day
    o     With  8  million  exposed  workers,   about  $2  billion  not  including
          workmen's compensation    (64 ) •
Ara children susceptible  to  performance  effects  of  noise?

Although  there   is   relatively   little   laboratory  evidence   to   substantiate
performance  degradation,  there have  been field  studies which  demonstrate  that
high noise  levels have been  correlated  with poor  performance  on  reading  rests
(65) and auditory discrimination  problems (66).  These effects were  found  • •> have
little  to do wich socio-economic class or IQ.  The significance of  these  effects
is  particularly  important  for  younger   children  who  through lack  of verbal
experience need  lower noise  levels in which to perform  in  order to -icv».lop  the
basic skills which contribute  to  cognitive  and language  development.
                                         5-5

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SLEEP  DISTURBANCE
Sleep disturbance is one of Che major  causes  of  annoyance due to noise.  If it
becomes  a  chronic problem, sleep  disturbance may  potentially lead  to health
disorders (67)*.
EFFECTS  OF  NOISE
How does noise interfere with sleep?

Noise, of course,  can make it difficult  to  fall asleep.  Noise levels can create
momentary disturbances of natural sleep  patterns  by causing shifts from deep to
lighter stages.  Noise may even cause awakening which the person may or may not be
able to recall.   (14)
Is the sleeper aware of all of his  bodily reactions  to noise?

He can be completely unaware of being affected but can have a disruption of total
sleep quality nevertheless.  Subjects  often forget and underestimate the number
of  times  that  they  awaken during  sleep  (88).   Loud noises  can continue  to
awaken or arouse  the  sleeper,  but  they may become  so  familiar  with the sounds
that they return to sleep very rapidly.
Vhat are the indirect effects of sleep disturbance?

A person whose sleep hss been disturbed severely may feel lethargic and nervous
during  his  waking  hours  and  aa;' be  unable  to  perform  at  his usual  level  of
efficiency (68).
* References are listed in Section 11,  e.g.:   (Ref.  67).
                                         6-1

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FALLING ASLEEP

What noise  levels can  delay  falling asleep?

At levels ot tC f> 50 dB (A-weighted),  some subjects  have  reported difficulty in
falling  asleep,  frequently taking over an hour.  The number of subjects having
difficulty  increases as  the  sound  level  increases (14).


AWAKENING


What noise  levels can  cause  awakening?

Studies  have  shown that  at  levels of  70  dB  (A-weighted)  or above.behavioral
awakening*  will most likely  occur  (14).


Do noises lasting a long period of time awaken more people Chan shorter noises?

The temporal pattern of exposure (i.e.;short or long duration) has a major effect
on awakenings  due  to  noise.   Short signals have  to  be  much  higher  in level  to
awaken as many people as a longer, steady noise.  (93, 68)

Are all  sounds equally effective  in awakening people?

Not all  sounds of the  same level  are equally  capable  of awakening  people.   The
character of some sounds causes them to awaken more people than other  sounds  of
the same level (68, 94).
   Behavioral  awakening -aeans  a  specific motor  or  veibal  response  (58
                                         6-2

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Does the background noise environment in which people are accustomed  to  sleeping
affect the number of nightly  awakenings  dje  to noise?

People living in higher background noise neighborhoods tend Co awaken less  Chan
people living in quieter background noise  neighborhoods.   (68, 94).

Do people awaken more at some times of  Che night  than aC  ochers?

The awakening effects of noise appear to be related  to the  time of occurrence of
exposure during Che night.   The probability of awakening  to noises  of  the  same
level is  slightly lower within two hours after retiring than when  it occurs later
in the night.  (68, 94).
AROUSAL  AND SUB-AWAKENING EfFECTS
Vhat st?ges of sleep does poise affect?

Laboratory subjects  appear  to be most sensitive to acoustic stimuli during  the
more  shallow  stages  of  sleep.  A  person  typically goes  through a cycle of  sleep
which  becomes progressively  deeper,  and the  stages of  this  cycle may vary  in
length of time.   These stages are reflected in EEC  measurements.  Heart rate
changes,   vasoconstriction,  respiration  changes,  electrodennal  activity,  and
moror  responses are  all  sensitive  to  noise during sleep.   (68)
                                     6-3

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CRITERIA  FOR  SLEEP  DISTURBANCE
Do  criteria  for  sleep disturbance  include  shifts   in  stage  of  sleep  and
behavioral awakening?
Examples of criteria pertaining  to sleep disturbance are displayed in Figures  6-1
and 6-2.  These figures,  which were adapted from a summary and analysis of recent
experimental sleep  data  as  related  to noise exposure (3),  show  a  relationship
between frequency of response (disruption or awakening) and  the sound level of an
intrusive noise.  In Figure 6-1, the frequency of sleep  disruption  (as  measured
by  changes  in  sleep stage,  including  behavioral awakening) is  plotted as  a
function of the Sound Exposure Level,  a time-integrated  measure  referenced to a
one second duration.  Similarly,  the frequency of awakening  is shown in Figure 6-
2.  Thus,  Figures 6-1 and  6-2  show that the probability of  two  types  of sleep
disturbance, within certain statistical limits,  may be predicted by  physical
indices of noise exposure.
      o
      h^
      O.
      cz.
      GO
      (/I
      u.
      o
      >•
      o
              40
50     50     70     80      90     100     110
      A-WEIGHTED SOUND EXPOSURE  LEVEL
                  FIG. 6-1.  PROBABILITY OF A NOISE  INDUCED
                             SLEEP  STAGE CHANGE
                                        6-4

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                  '55       65     "75    '85      95    105     115
                  A-WEIGHTED  SOUND  EXPOSURE  LEVEL  (decibels)
                FIG. 6-2.  PROBABILITY OF A NOISE INDUCED
                           AWAKENING
How does sleep disturbance varv with noise level?

Generally, the higher the noise level Che greater the probability of a response
(63).  Thiessen found that  there  was  a  5 percent probability of subjects being
awakened by peak levels  of 40 dB (A-weighted  level)  and  a  30 percent probability
at 70 dB.   If  EEC changes  are also considered, these probabilities increase to 10
percent at 40 dB and 60  percent at 70 dB (39).
                                        6-5

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Do the  number of  noise  peaks have  any  effect on  the  ability of  the noise  to
interfere with sleep?

If the  number of  sound  peaks increases,  the person will  take longer  to  fall
asleep  even  if the  average  sound  level  decreases  (14).   However, continuous
or very frequent noise throughout the night, even as high as 95 dB (A-weighted),
appears to cause little change in  the average duration of the sleep stages,  since
such  stages  are disturbed more  by  peaks  that  vary widely from  the background
ambient level  than  by high continuous levels  alone  (68).
Does the quality of the  sound have any effect on the  ability of noise to interfere
with sleep?

Inherently meaningful sound such as one's name or sound that acquires meaning by
instructions or conditioning can awaken a  sleeper at lower intensities than those
required  for meaningless or neutral sounds.  Unfamiliar sounds may awaken people
at  a lower  level  than familiar  ones.   (68,  70)

Are the sex and age  of  the  sleeper  factors  in disturbance  of  sleep by noise?

Several investigacors have reported that middle-aged women may be less sensitive
to noise during sleep.   (69)  In general,  though, the older the subject, the more
likely  he is  to respond to noise  while sleeping (68).  Young children,  on  the
other hand, appear  to be less affected  by noise  in  all  stages  of  sleep  (70).
Does  the amount  of  time  asleep  affect  the  response  to noise?

Arousal  is more  likely to  occur  after  longer  periods  of  sleep (71),
                                        6-6

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Does sleep deprivation have an effect on the disturbance of sleep by noise?

Sleep after prolonged periods  of  sleep deprivation consists of increased tine in
stages Delta and REM.  This causes an increase in the thresholds for arousal and
stage change (63 ) =     Overall,  sleep-deprived individuals require more intense
auditory stimuli to awaken than do normally rested persons (71).
Is sleep disturbance by noise seen as a problem by the population in general?

Survey data show  that  sleep  disturbance is often one  of  the  principal reasons
given for noise annoyance (14).


Can sleep disturbance cause long-term problems?

Sleep is  thought  to be a  restorative  process  during which organs  of  the body
renew their supply of energy and  nutritive elements.  Since noise can disrupt the
sleep process,  it may take its toll on health.   (14)
                                        6-7

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SUBJECTIVE RESPONSE
Conclusions  concerning  the factors  that  determine  an  individual's  subjective,
psychological response to noise are difficult to derive  since individuals vary so
much in their reaction to noise.   Clearly, more research is needed to assess this
complex topic fully.
MENTAL, PSYCHOLOGICAL EFFECTS
What  kind of  mental  or psychological  effects  can occur with  excessive  noise
exposure?

Excessive  noise  exposure   can  bring  about  a  wide  variety of  psychological
responses  or  symptom?  in the individual.   A person may respond with anger,  or
experience  symptoms such  as anxiety,  irritability,  and/or  general  emotional
stress.  Noise may  negatively affect work performance because of reduced worker
morale  and motivation.    D.istraction  and poor judgment may result from mental
fatigue.   (14)*
 Is excessive noise exposure related fo mental illness?

 The answer  to  this remains unsolved.  Studies have shown that residential areas
 exposed  to  high noise levels may have a higher incidence  of mental illness among
 their  residents, however  the evidence is inconclusive.  One study thit examined
 admissions  of  residents         ne&r London's Heathrow Airport   to a psychiatric
 hospital  suggests  that  the prevalence  of  mental  problems  was higher  in  the
 population  nearest the airport (90).  On  the  other hand, a Swiss  study  looking at
 the  mental  health  status  of  residents  near  three  Swiaa  airports   found  no
 signficant  relationship between  minor  psychiatric  illness  and noise exposure
 (72).

 * References are listed in Section  11, e.g.:  (Ref.  14).
                                         7-1

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What physical qualities of noise affect a person's subjective response?

The  physical  attributes  of  noise  that  can  affect  an  individual's  subjective
response include:  apparent  loudness or  intensity,  spectral  shape,  presence of
discrete  frequency  components,  abruptness  or  impulsiveness,  intermittency,
duration, and temporal variations (14).
Besides the physical attributes of  the noise  itself,  vnat  other aspects of the
exposure situation affect the individual's response?

Among the factors that affect an  individual's  response  to  noise are contextual
factors such as:  the time of day, the activity interfered  with, the ability to
control the source,  and the information content  of  the noiss.  Response may also
be affected by personal factors  such as  previous experience with noise exposure
or socio-economic and educational  status.   (14,4,9)
What is the best weighting system to use for analysis of individual subjective,
psychological response?

In most cases,  the             A-weighting scheme can be used  to study individual
response to  noise.   Figure  7-1   shows  how  the A-weighting  network  on a sound
level meter discriminates sounds  at different frequencies compared to the B and
C-weightings.  A recent study has  indicated that the D and E weightings generally
perform  somewhat better  than A-weighting.    Computational  schemes,   such  as
Stevens' Mark VI  and Mark VII loudness calculation procedures, Zwicker's loudness
calculation procedure,  Perceived Noise Level, etc.,  are typically  superior to the
frequency weightings.   In the long run however, none of these  other weightings or
calculation schemes  need to displace the simple A-weighting which has the added
advantages of ease of use, public acceptance, and reasonable accuracy (73).
                                        7-2

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     a -15
     1-20
       -25
      > -30
     i -35
       -4Q
       -50
            /
Frequency Responses
  for Sound Level
                                 Weighting Characteristics
          20      50    100    200      500   1000   2000    5000  'O.COO 20,000
                                   Frtqutncy lwi)
             FIG. 7-1.   FREQUENCY RESPONSES  FOR  SOUND  LEVEL
                         WEIGHTING CHARACTERISTICS.

What is meant by  the  teras "phon" and "sone",  and what is  their  application to
subjective response?

Phons and sones are used Co measure  or  rate  loudness  (the subjective impression
of  the  magnitude of  a sound).   A  pnon is  the  unit  of  loudness  level.    It
is  intended  to  be equivalent  to  the decibel level of  a  1000  Hz  reference  tone
judged  equally   loud  to the  sound  being  evaluated.   Figure  7-2  shows  equal
loudness contours as a function of frequency which demonstrates the relationship
between loudness  level  (in phons)  and  intensity (in  decibels).

The sone  is  a  linear  measure of loudness.   The loudness of one sone equals the
loudness of  a 1000 Hz  tone at  40  dB  sound  pressure level.  A sound  judged to be
twice as loud as  a 1000 Hz tone  at 40 dB equals 2 sones;  half  as  loud, 1/2 sone,
etc.  Generally,  in increase  of  10 dB is equivalent  to  a  doubling  of sona value,
and the judged Icudness.  The Stevens method  and Zwicker procedure  both calculate
sone values  of complex  wide  band  sounds.
                                          7-3

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      a
      •3
          120
          20
                                      500   1000
                                    Frequency
                                                         5000   10000
                         FIG. 7-2.   EQUAL LOUDNESS CONTOURS
Are there any particular noises that are more annoying than others?

Sounds of 2 KHz or higher (especially those with discrete  frequency  components)
are generally the most annoying and disruptive,  although  noises  that  are  abrupt,
intermittent, or  fluctuate  with time  can  be very  annoying  as  well  (14).   In
general, the louder the nosie the more annoying it is likely to be (14).
Are there any  special  populations  that  are particularly annoyed or  bothered by
noise?

A  number  of variables  aay affect  individual susceptibility  to  noise.   These
include personality factors, psychological factors, state of health, etc.
Special populations  that  are  particularly sensitive have not  been  identified,
however,  and  research  needs to be performed  to identify these groups,  if any.
                                         7-4

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 Does personality  play  a  role  in  individual  response  to  noise?

 Social  surveys  have indicated wide individual variations in response to noise.
 It appears that personality does play some part in a person's subjective  response
 to noise, although  the exact natura of the relationship  is too complex to assess
readily.   Some  studies  have concluded  that  those  with a  fairly  high  level of
 empathy,  intelligence,  and creativity uay be more sensitive to noise then  most
 (75).
 Hov  do  individuals  alter their behavior  in order  to  cope  with  noise?

 People  may  either   take  direct  physical  actions  or  make   indirect   mental
 adjustments  to  cope with  noise.   For  example, people may  spend  less  time
 outdoors,  keep their windows  closed,  take sleeping pills, use  earplugs,  spend
 less time  talking and socializing,  or  complain to government officials.   On the
 other hand,  they  might  direct  their  anger  at a noise inward and blame  themselves
 for  being  bothered by it.  They may perhaps deny there is a problem and attempt to
 stop responding emotionally  to it.   They may even project  their anger at  a noisa
 source  to  a  person  incidentally associcated with it.  (76)
  Can  noise  cause an individual to exhibit anti-social behavior?.

  Noise  can  cause peop;eto exhibit sucn anti-social behavior as aggression and
  violence,  though they would not normally do so.            .    Certain extreme
  incidents  that have  been  reported,  for  example,  include  a business  executive
  shooting at  nearby water-skiers, or  a  usually  quiet, night  clerical worker
  shooting and  killing  a child  playing outside his  appartment.   Both  examples
  provide  anecdotal illustrations of effects  on  behavior  presumably attributed  to
  noise  (1*0.   There have also been lab studies which show that excessive noise may
  reduce social  interaction, social responsibility, and  verbal  disinhibition,
  diminish helping behavior,  and increase  aggressive  response.   (77,  78,  79)
                                          7-5

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Can noise lead Co reduced social interaction and enjoyment?

Besides  the  obvious  impairment in  social  interaction  associated  with noise-
induced hearing loss, living in a noisy  environment  oiay lead  to  what  could be
referred to as  a   noncommunicative  life-style.   This  is a life—style  in which
social  interaction  is  avoided  and  communication is  minimized  due  to noise
interference (31).
                                        7-6

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COMMUNITY  RESPONSE
This  section concerns  average community  response to  noise as  determined by
community surveys, and other measures of annoyance such as complaints.
How does noise  annoy?

Noise  by  definition is unwanted  sound.   It is an  intrusion  on  one's sense of
privacy.  Noise can be an emotional strain and a source of great frustration when
the noise is beyond a person's control.  Noise may interfere with a broad range
of human  activities,  the overall  effect of  which  is  to cause annoyance.   Such
activities  include:

    1.    Speech Communication in  Conversation and Teaching
    2.    Telephone Communication
    3.    Listening to Television  and Radio  Broadcasts
    4.    Listening to Music
    5.    Concentration During Mental Activities
    6.    Relaxation
    7.    Sleep
To what degree does noise cause neighborhood  dissatisfaction?

The  HUD Annual  Housing  Survey (1975,  1976)  indicates that noise  is the most
frequently cited undesirable neighborhood condition, surprisingly ranking higher
than crime.  Noise  is often given as the reason for residents wanting to move from
their neighborhoods.   (4).*
* References are  listed  in Section  11, e.g.:  (Ref. 4),
                                       8-1

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How is community response measured?

Community response to noise is  usually  studied  through social surveys.  A number
of social surveys have been conducted world wide to determine the extent of the
noise problem as well as to assess the response of the people to specific noise
sources.  These studies attempt to predict,  on  an  aggregate basis, the degree of
annoyance or other effects  that  can be expected by the community  at varying noise
levels.   The  average  response of  the community is used  because  it  is  very
difficult to predict the response  of any given individual.
Are complaints a good indicator of the community noise problem?

Another way  of assessing  community  response is  through complaints  and  legal
actions.  However, many other economic, political, and social factors influence
the filing of complaints.  So the  quantification of complaints cannot be used as
definitive expressions of community response.  Figure 8-1  shows the correlation
of  community  complaint  reaction  to   noise  after the  noise exposure  has  been
adjusted for factors such as time  of  year  (windows open or closed), duration and
frequency of intruding noises, presence of pure  tones or impulses, etc.
                                        a-:

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m Community Reaction
Vigorous Action
Widespread Threati
of Legal Action. Strong
Appeals to Local
Officials to Stop Noisa
Widespread Complaints.
Individual Threati of
Legal Action
Sporadic Complaints
No Overt Reaction
Although Noise is
Generally Noticeable

• • * *** f.
• rt .»-- *
*•!•»•
....» .. .,
••*•! •! *• • t
. ., ? -
J
?» • I'M**
i - T ', * i 1,1,'
                          40        50       60        70       80       90
                          Adjusted Outdoor Day/Night Sound Level of Intruding Nois* in dS

        FIG. 8-1.   COMBINED DATA FROM COMMUNITY CASE STUDIES
                    ADJUSTED FOR  CONDITIONS OF  EXPOSURE
                    SOURCE:   Ref. 5
Why is "percent highly  annoyed"  used as  an index of community annoyance?

The use of the percentage  of  exposed persona who race themselves highly annoyed
is  used  because  it  is  the  most  stable  indicator  of  annoyance.   Persons who
perceive their noise exposure as an extreme annoyance have littla difficulty in
sorting  their feelings out  from  other  non-acoustic  variables  which  tend to
scatter  responses  on   surveys  which  try  to  determine  the median  community
response.  Because the highly annoyed individual exhibits a definitive response,
a clearer  and more meaningful  relationship between  outdoor  noise exposure and
annoyance can be  seen through  this index.   (80)   3y  looking at this index, one also
has an idea of the magnitude of the annoyance problem by looking  at Che worst case.
Nevertheless,  it  should be  recognized  that many more poeple are  annoyed, but to &
lesser extent, than would  be  indicated  by the descriptor "bighly annoy»d".
                                        8-3

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What,  if  any,  distinction  should  be  made  between individual  and  collective
response?

It  should be  kept  in mind  that  community  response  to  noise  is  based  on
statistical averages  since  it  is known  that response  to  noise varies  greatly
among individuals.
Based  on  the  Levels  Document,  what  is   the  relationship  between  annoyance,
complaints, and community reaction as a function of day-night sound  levels?

According  to  the  EPA Levels  Document,   (5)  approximately  17  percent  of  the
population will be highly annoyed at  an L,  of 55 dB,  and  over  40 percent of the
population will be highly annoyed ^£  the L, exceeds 70 dB, the maximum safe level
EPA has  identified to  protect against  a risk  of hearing loss.   The lelationship
between noise and annoyance given in   the  Levels  Document is  based largely on the
results of surveys around airports.   These estimates  have been crticized because air-
craft noise  is not present  in many urban  areas.   CompU^C3  occur at a much lowej.
rate than annoyance,  and generally do  not become evident until the noise levels are
rather high.   At  an  L,  of 70  dB, approximately ten  percent can  be expected to
complain, while 25 to 40 percent  of the population will be annoyed.   At  an L.  of 55
                                                                         dn
dS, complaints are expected to be almost  non-existent.  Vigorous community action
can be expected as the L,  exceeds 70 dB.
                        an
What is the late1 t TJteria showing the  extent of community annoyance thct can be
expected from givon levels of noise?

Schultz (30) synthesized  results  from nineteen  social surveys of annoyance  and
found a remarkable consistency.  The synthesized data yields a  somewhat different
result  from  that  relationship depicted  in the  EPA Levels Document.  Figure  3-2
from   Shultz  shows   Che   close   clustering   of  annoyance  curves  from  uany
transportation sources.   Generally,  data  synthesized from prior social  surveys
on noise as  displayed  in  Figure  3-2  indicate Chat  very  few  people (on  average
                                       8-4

-------

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	 rS£N'a, A, C u966)

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i 1
-° so so ;o so 50
L, (decibels)
an
FIG. 8-2.   SUMMARY  OF AXN'OYAN'CE DATA FROM  12  Sl'R'.T.'S
            WITH  DATA SHOWirG CLOSE AGR£i:-E>~.
            SOURCE:   Ref.  30
                       3-5

-------
three to four percent) will be highly annoyed  by noise at or below a  level of about
L   =55 dB.   However, about 16 percent of the population will be highly annoyed
 dn
bv noise at about a level of L,  =65 dB; twenty-five percent of the population
 1                            dn
will be highly annoyed at L   = 70 dB; and thirty-seven percent of the population
will be highly annoyed as the noise level reaches  Ldn  =  75 dB.  Twenty to thirty
percent of the population are  apparently imperturbable  and  not bothered even
by    high  noise  levels.   (81)   The Committee  on Hearing,  Bioacoustics,  and
Biomechanics  (CHABA) has indicated  that  these data  are       ap  to  date  and has
included them in its guidelines for  environmental impact  statements  on noise
(81).

Are  there  other  measures  which are  considered  good predictors  of community
annoyance?

The Urban Noise  Survey found  that activity interference  £of  speech, sleep, etc.)
is a good predictor of annoyance.   Speech interference is one of the  most widely
perceived  effects of environmental  noise.    Another    predictor  of community
annoyance is population  density.  Higher  population density  areas generally have
higher noise  levels, thus the annoyance  is greater.   (82)
Vfhat other factors may influence personal reaction to noise?

Social surveys have shown that  the  following  factors may contribute  to community
noise annoyance;

    1.    Fear  associated  with  activities  of  noise  sources (such  as  fear  of
          crashes in the case of aircraft noise)

    2.    Socioeconomic status and education level
                             
-------
    4.     Attitude of  the  community's  residents  regarding the contribution of
              activities associated with the noise source to the general well-
          being.

    5.     The extent to which residents  of  the  community  believe that the noise
          source could be controlled      (14)
RESULTS  FROM THE  URBAN" NOISE  SURVEY
A total of 2037 people  (726 men,  1275 women) were  interviewed for this survey.
Twenty-four sites were selected to represent areas with different noise levels
and population densities.   Sites where either aircraft noise or highway noise
predominated were excluded.
How does noise exposure relate to general  neighborhood  satisfaction?

Comparing responses from people in high noise  exposure  areas  (mean L^  • 70 dB)
and low noise exposure areas (mean L,  » 54.6  dB),  it was  found  that 34 percent
fewer  people  in  the  high  exposure  areas described their  neighborhood  as  an
excellent place  to live,  and  24  percent  more people  in these  areas described
their neighborhood as only  satisfactory.  Seventeen percent more people in the
high exposure areas responded that they had  been annoyed by  noise.   (82)
                                        8-7

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What was the relationship  between noise  level and annoyance shown by the survey?

             Noise Level (L. )          Percentage of Population Annoyed
             _____	-an—                  w       '

                    55                                 7
                    60                                12
                    65                                17
                    70                                23
                                                                    (82)

How does population density affect  community response to noise?

High population density is  usually associated  with  higher  noise levels.  It is
not surprising then that people in  high density areas are more annoyed by noise
than people in low density areas.   In  the Urban Noise Survey, respondents living
in high density areas  reported 20 percent more  listening interferences, 9 percent
more conversation  interferences,   and  9 percent  more sleep  disturbances  than
respondents in low density areas.   (82)
Can socioeconomic status be related to annoyance from noise?

Generally, people in     upper income brackets are less likaly to be annoyed by
noise because they can be more selective in  deciding  where  to  live.  Since peace
and quiet are important selection factors, the wealthy  are more likely to reside
in quiet neighborhoods and therefore can avoid annoyance from noise.
How does the time  of day, season, location (indoors  or outdoors) affect community
response to noise?

In relatively noisy areas where  the L,  exceeds 60 dB.people consider noise  to be
more obtrusive in the  evening and night hours.  People are more annoyed by noise
in the summer, presumably because windows are open, and there may be additional
                                        8-8

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noise sources such as air conditioners and lawnmowers .  The results of the survey
also show that people are more annoyed by  noise  indoors  than outdoors.  (82)
What are some of the major conclusions drawn  from  this  survey?

    o     Exposure to noise typical of many urban (non-aircraft  and non-highway)
          environments  produces  widespread annoyance,  speech interference, and
          sleep disturbance.

    o     A  strong relationship  was  demonstrated between  exposure level and the
          proportion of a  community  highly annoyed by noise.

    o     The prevalence of speech interference  is an especially good predictor
          of annoyance.

    o     Population density  is  an important  correlate  of noise exposure.

    o     The  number  cf  complaints  about  noise  is a  poor predictor  of the
          prevalence of annoyance.

    o     Demographic   factors  alone are  relatively poor  predictors  of  noise
          annoyance.

    o     Freedom   from   noise   exposure  is   a   civta^onent  of   neighborhood
          satisfaction, and quiet  is highly valued.
                                        8-9

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HEALTH AND WELFARE ANALYSIS
What methods are    used     to ascertain noise impact and predict the benefits  of
implementing noise reduction measures?

A number of current state-of-the-art criteria of noise effects on people may  be
employed Co gauge the impact of noise and the benefits to be gained  by reducing
noise.  Criteria in general use are  those representing Lhe amount of  annoyance  to
be expected at  different  levels of noise,  the  potential  for interference with
speech .communication  and the probability of disturbed  sleep due  to  noise.  This
is not to say that other noise effects do not occur.  There  are indications of the
presence of many other effects of noise.  However, cause-effect  criteria have not
been derived for these other effects, and knowledge is generally insufficient for
health and  welfare  analysis purposes.   Nevertheless,  the  criteria   for general
adverse  response  (annoyance)  may  be used as  a  basis to  infer  these remaining
effects of noise on people.  (8, 81)   •
What is "Level-Weighted Population" and how is it used?

Level-Weighted  Population  (LWP)  (81)  expresses  both  the  extent  and   the
severity of a r.oise impact.  The extent of impact  refers  to  the number of people
who are adversely  affected,  while the severity represents  the  degree to which
each person is affected.   LWP  provides a simple,  single number used to compare
benefits of different noise reduction options.

It has been determined that an outdoor L, value of 55  dB  (or an indoor L   of 45
                                        dn                             dn
dB) represents the lower threshold of noise jeopardizing the health and welfare
of people.   In  the range abovp  these  levels,  noise may be  a  cause of adverse
physiological and  psychological effects.  These effects often result  in annoyance
and community action.   Noise ab_qye ^  ?5  dB  may^  ln tim&f cause hearinK  logg
and the possibility of other severe health effects.
  References are listed in Section li,  e.g.:  (Ref. 8).
                                          9-1

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The computation of L.WF allows one to combine the number of people  jeopardized by
noise above an  L^n of 55 dB with the  degree  of  impact at different noise  levels.
Figure  9-1  is  a  pictorial representation of the LWP  concept.  The  circle  is  a
noise source  which  emits noise to a populated  area  represented by the figures.
The  various  partial  amounts of  shading  represent  various  degrees  of  partial
impact by the noise.  Note that those  people  closest  to the noise source are  more
severely threatened.  The  partial impacts are then sucnmed to give  the equivalent
noise  impact.   In  this  example, six people who  are adversely affected by the
noise (partially  shaded) results  in a Level-Weighted Population of two (totally
shaded).
           FIG.  9-1.    LEVEL WEIGHTED POPULATION:   A METHOD TO
                       ACCOUNT FOR THE EXTENT AND  SEVERITY OF
                       NOISE IMPACT.
                                         9-2

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SUMMARY OF HUMAN  EFFECTS  FROM  VARIOUS  OUTDOOR

NOISE  LEVELS
The  following five tables present information  on  the  possible effects on people

caused by outdoor day-night noise levels  of  55, 60, 65,  70, and  75 decibels.


   Summary of Human Effects for Outdoor Day-Night  Sound  Level of 55 Decibels
      Type of Effect

Hearing Loss

R.'.sk of nonauditory disease
   (stress)

Speech** - Indoors
         - Outdoors
                Magnitude of Effect
Will not occur

*
No  disturbance  of  normal  conversation.    100
percent sentence  intelligibility (average)*with a
5 dB margin of safety

Slight  disturbance  of normal  voice*  or  relaxed
conversation   with    100   percent    sentence
intelligibility (average)  at 0.35  meter
High Annoyance
Overt Community Reaction
Attitudes Towards Area
                               99 percent  sentence  intelligibility  (average)  at
                               1.0 meter
                                                         or
95 percent sentence intelligibility (average)  at
3.5 meters

Depending on  attitude  and other  non-acoustical
factors,   approximately    4   percent   of   the
population will be highly annoyed.

None expected;  7  dB below level  of  significant
"complaints and threats of legal action," but  at
least 16   dB  below "vigorous  action"  (attitudes
and other non-acoustical  factors may modify this
effect)

Noiso considered  no more  important than various
oth^r environmental factors
 *  and ** See the notes on page 10-6.
                                        10-1

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   Summary of Hunan Effects for Outdoor Dav-Nisht Sound Level of 60 Decibels
      Type of Effect

Hearing Loss

Risk of nonauditory health
  effects (stress)

Speech** - Indoors
         - Outdoors
          Magnitude of Effect
Will not occur
No disturbance of normal conversation.   100
percent  sentence  intelligibility  (average)
with no margin of safety

Moderate  disturbance  of  normal  voice  or
relaxed   conversation   with   100   percent
sentence  intelligibility  ('average)  at  0.2
meter
                                                         or
                                    99    percent    sentence
                                    (average) at 0.6 neter
                            intelligibility
                                                         or
High Annoyance
Average Connsunity Reaction
Attitudes Towards Area
                                    95    percent'    sentence
                                    (average) at 1 meters
                            intelligibility
Depending   on   attitude  and   other   non-
acoustical  factors, approximately 9 percent
of the population will be highly annoyed.

Slight  to  moderate;  2  dB  below  level  of
significant "complaints and  threats of legal
action," but at least 11 dB below "vigorous
action" (attitudes and other non-acoustical
factors may modify this effect)

Noise nay be considered an adverse aspect of
the community environment
* and ** See the notes on page 10-6.
                                         10-2

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    Summary of Human Effects for Outdoor Day-Night Sound Level of 65 Decibels
      Type of Effect

Hearing Loss

Risk of nonauditory health
  effects (stress)

Speech** - Indoors
        - Outdoors
           Magnitude of Effect

Will not occur
Slight disturbance of normal conversation 99
percent  sentence  intelligibility (average)
with a 4 dB margin of safety

Significant disturbance  of  normal  voice or
relaxed   conversation  with   100   percent
sentence  intelligibility  (average)  at  0.1
meter
                                                         or
                                    99    percent    sentence
                                    (average)  at 0.3 meter
                            intelligibility
High Annoyance
Average Community Reaction
Attitudes Towards Area
                                    95    percent    sentence
                                    (average)  at 1.2 meters
                            intelligibility
Depending  on   attitude,  and   other  non-
acoustical    factors,    approximately   15
percent  of  the  population  will  be  highly
annoyed.

Significant;  3 dB above  lev-si of significant
"complaints and  threats of  legal action,"
but at  least  7 dB  below "vigorous action"
(attitudes and other non-acoustical  factors
may modify this effect)

Noise  is  one  of  the  i portant  adverse
aspects of the community environment
* and ** See the notes on page 10-6.
                                        10-3

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   Summary of Human Effects for Outdoor Dav-Night Sound Level of 70 Decibels
      Type of Effect

Hearing Loss

Risk of nonauditory health
  effects (stress)

Speech** - Indoors
        - Outdoors
High Annoyance
Average Community Reaction
Attitudes Towards Area
          Magnitude of Effect

Will not likelv occur
Slight  disturbance  of  normal  conversation
approximately     99     percent     sentence
intelligibility (average)

Significant disturbance  of  normal  voice  or
relaxed   conversation   with  100   percent
sentence intelligibility (average)  possible
only at distances less than .06  meter
                                                         or
                                    99    percent    sentence
                                    (average) at 0.2 meter
                            intelligibility
                                                         or
95    percent    sentence '   intelligibility
(average) at 0.6 meter

Depending   on   attitude  and   ocher   non-
acoustical    factors,    approximarely    25
percent  of  the  population  will  be  highly
annoyed.

Severe;  8  dB  above  level  of  significant
"complaints  and  threats of  lezal action,"
but  at  least 2  dB  below  "vigorous action"
(attitudes and other non-acoustical factors
may modify this effect)

Noise  is  one  of  the most  important adverse
aspects of the community environment
* and '•** See the notes on page 10-6.
                                        10-4

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   Summary of Human Effects for Outdoor Day-Night Sound Level of 75 Decibels
   Tvoe of Effect
Hearing Loss
Risk of nonauditory
  health effects
     (stress)

Speech** - Indoors
         - Outdoors
                Magnitude of effect

May begin  to  occur  in sensitive individuals, depending
on actual noise levels received at-ear.
Some  disturbance  of  normal   conversation.    Sentence
intelligibility (average) approximately 98 percent

Very significant disturbance of normal voice or relaxed
conversation with   100 percent sentence intelligibility
not possible at any distance
                        99 percent  sentence  intelligibility  (average)  at   0.1
                        meter

                                                  or

                        95 percent  sentence   intelligibility  (average)  at  0.4
                        meter
High Annoyance
Average Community
  Reaction
Attitudes Towards
  Area
Depending on attitude and other non-acoustical factors,
approximately  37   percent  of  the  population will  be
highly annoyed.

Very   severe;   13   dB   above  level   of   significant
"complaints and threats of legal action" and at least 3
dB  above  "vigorous  action"  (attitudes and  other non-
acoustical factors r?,ay modify this effect).

Noise is likely to be the most important of all adverse
aspects of the community environment.
* and ** See the notes on page 10-6.
                                       10-5

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The  following  notes should  be kept  in  mind  when examining the  preceding  five
Cables:

*    Research implicates  noise  as  a  factor  producing  stress-related  health
     effects such  as heart  disease, high blood pressure and stroke, ulcers  and
     other  digestive  disorders.    The  relationships  between  noise  and  these
     effects have  not  yet been quantified,  however.

**   The speech effects  data in these tables  are  drawn from the Levels  Document
     (5), as follows.   Indoor  effects are based on Table 3, and  on Figure  D-l,
     with 15 dB added to the indoor level to obtain the outdoor reading.   Outdoor
     effects come  from Figure  D-2,  using L.  (as  determined with Figure  A-7).
     Both Figures  D-l  and D-2  are  based  on  steady noise, not on L  .  Table  D-3
     shows that for fluctuating noise  the average percent  interference  is lower
     than for steady noise  of  the  same L  .  The values given in this  report are
     the best estimates  of  the interference.
NOTE;   Outdoor  speech intelligibility estimates assume  70  dD  (67  dBA)  level  of
        speech.
                                        10-6

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 REFERENCES
 1.   United  States  Public Law  92-574,  "Noise Control  Act  of  1972,"  (October 27,
     1972).

 2.   United  States  Public Law  95-609,  "Quiet Communities  Act of  1978,"  (January
     19,  1973).

 3.   Bachmann, W.,  "Health and Disease.  Critical Fnoughts on the Health Concept
     of che  World Health Organization," Munchen  Med.  Wochenschr,  Vol.  119,  (May
     18,  1977),  p.  349.
 4.   U.S.  Environmental  Protection Agency,  "The Status of Noise  Control  in The
     United  States:   State and Local Governments,"  (prepared by  Dr.  Clifford R.
     Bngdon,  Dept. of City  Planning,  Georgia Institute  of  Technology),  (April
     1978),

 5.   U.S.  Environmental  Protection Agency,  "Information  on Levels  of  Environ-
     mental  Noisi Requisite to Protect  Public Health and Welfare with an Adequate
     Margin  of Safety,"  550/9-74-004,  (March 1974).

 6.   U.S.  Environmental  Protection Agency, "Protective Noise  Levels (condensed
     version of  EPA Levels Document)," 550/9-79-100,  (November 1978).

 7.   U.S.  Environnental  Prott tion Agency, Office  of Noise Abatement  and  Con-
     trol,  Noise in  America,  Washington,  D.C.,  in preparation.


 6.   Schori,  T.  R. , "A Real World Assessment of Noise  Exposure," EPA-AI-31L Report
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 9.   U.S.  Environmental  Protection Agency,  Toward a National Strategy  for N'oise
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10.   Federal Register, Vol.  42,  No.  23,  (February 3,  19771,  pp.  6722-6723.

11.   U.S.  Environmental  Protection Agency,  "Effects  of Noise on People,"  NTID
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12.   Davis,  H.,  and  Gilvenian,  S.  R. , Hearing  and Deafness, New York:   Holt,
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13.   Newby,  H.A., Audiology. Enjiewood Cliffs,  M^w Jersev:  Prentice Hall, Inc.,
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14.   U.S.  Environmental  Protection Agency,  Public  Health and WeUare  Criteria
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                                       11-1

-------
15.   Royster,  L.  H. ,  "Potential  Hearing Compensation  Cost,   Percent  of  the
     Population Exceeding Different Frequency Low Fence  Hearing Threshold  Level
     Combinations  and Equivalent Frequency Low Fence  Combinations  for  Black  and
     White, Male and Female Population,"  paper presented befora the Acoustical
     Society of America, (May 1978).

16.   Martin,  F.,   Introduction   to  Audiolo|y, Englewood  Cliffs,   New  Jersey:
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17.   Taylor, W., et  al.,  "Study  of Noise and Hearing in Jute Weaving," Journal of
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18.   Henderson, D.,  ed., et al., Effects  of  Noise  on Hearing,  New York:   Raven
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19.   Schein, J. D.,  and Deck, M. T.,  The  Deaf Population of  the United  States,
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20.   Kryter, K., The Effects  of  Noise on Man, New  York:   Academic Press,  (1971).

21.   Hamernik, R.  P., et al., "Impulse Noise and Synergistic Effects  Aggravate
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22.   Hodge, D. C., and  Price, G. R.,  "Hearing Damage Risk  Criteria,"  Noise  and
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23.   Cuniff, P. F.,  Environmental  Noise  Pollution,  New York:   John Wiley  and
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24.   Ward,  W.  D.,  et  al.,  "Temporary Threshold  Shift Produced  by  Intermittent
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25.   Federal Register,  Vo.  36, No.  105,  (May 21,  1971),  p.  10158.

26.   Spoor, A., "Presbycusis Values in Relation to Noise-Induced Hearing Loss,"
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27.   Cohen, A., Anticaglia, J.,   and Jones, H.  H.,  "'Sociocusis' - Hearing Loss
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     1970), pp. 12-20.

28.   Rosen, S., "Presbycusii; Study of a Relatively Noise-Free Population in  the
     Sudan," Annals  of Otology. Rhinology,  and Laryngology,  (1967), pp.   727-743.
                                        11-2

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29.   Rintleman,  W., and  Bienvenue,  G., "Rock  Music  and Noise-Induced  Hearing
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     vention,  (October 29  -  November  1,  1976).

30.   Whittle,  L.  S.,  and Robinson, D. W.,  "Discoteqae  and  Pop Music  as a Source
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     Physical  Laboratory,  NPL Acoustics  Report  AC66, (March  1974).

31.   Miller,  J.  P., "The Effect  of Noise on People,"   Journal of  tha  Acoustical
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32.   Mills, J. H.,  "Noise  and Children - A  Review of Literature,"  Journal of  the
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33.   Cohen,  A.,   "Effects  of Noise on  Psychological  State", ASHA Proceedings,
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34.   Suter,   A.,   and   Von Gierke,  H.   E.,   "Evaluation  and  Compensation   of
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35.   American  Academy  of Ophthalmology  and Otolaryngology, Committee  on Conser-
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     (1965),  pp.  740-751.                                                     )

36.   AAOO,  "Guide for  Evaluation of  Hearing Handicap," Journal of the American
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37.   "Criteria for  a  Recommended  Standard  Occupational  Exposure  to  Noise,"
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38.   Ginnold,  R.,  "Occupational  Hearing Loss:  Workers  Compensation in State  and
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39.   U.S. Department of Housing and Urban Development,  "Annual Housing Survey:
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40.   Ando,  Y., and Hattori,  H., "Statistical  Studies  on the  Effects  of Intense
     Noise During Human Fetal Life," Journal of Sound and Vibration,  (1973),  pp.
     101-110.

41.   Selye, H.,  The Stress of Life, New York:   McGraw  Kill  Book Co.,  (1956).

42.   Peterson, EC  A., e£  al.,  "Noise  and  Cardiovascular  Function  in  Rhesus
     Monkeys,"  Journal of Auditory Research, No.  15,  (1975), pp. 234-251.
                                       11-3

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43.  Jonsson, A., and Hansson,  L., "Prolonged Exposure to a Stressful Stimulus as
     a Cause of  Raised  Blood  Pressure in Man,"'The lancet. (January 1977), pp.
     86-37.                                     	

4«,  Frerichs,  R. R. ,  Beeman,  3. L. ,  Coulson.  A. H.  "Los  Angeles  Airport.  N'oise
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     Public Health,  Vol. 70, No. 4,  (April 1980) pp.  357-361.

45.  Geber,  W., "Cardiovascular and Teratogenic Effects  of Chronic Intermittent
     Noise Stress," ed. Welch,  3. L.  and Welch,  A.  S. ,  Physiological Effects of
     Noise, (1970), pp. £5-90.

45.  Edoonds.   I...  Layde,  P.  M. ,   and  Erikson  J.  ?.,  "Airport  Noise  and
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     243-247.

47.  Tobias,  J.  V.,  and  Irons,  F.  X,,  "Reception  of  Distorted  Speech,"  in
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     Problem. Dubrovnik, Yugoslavia,  May  13-13, 1973.   Washington,  ?.C.:   U.S.
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48.  Suter,  A.   H.,   "The  Ability  of Mildly  Hearing-Impaired Individuals  to
     Discriminate  Speech  in  Noise,"  Washington,  D.C.:    U.S.  Environmental
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49.  Durrant, J. D., "Anatomic and Physiologic Correlates of the Effects of Noise
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50.  Webstar,  J. C.,  "The Effects   of  Noise  on  the Hearing of  Speech,"  in
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51.  Carpenter,  A.,   "Effects   of Noise on Performance  and  Productivity,"  in
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52.  Harris, C.  S. , "The Effects  of  Different Types  of Acoustic Stimulation :~
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53.  Guliaa, E., "Noise as an  Occupational Hazard:  Effects on  Performance Level
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54.  Sroadbent, D . E., "Effects of Noises  of High and Lev Frequency in Behavior."
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                                        11-4

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55.   Boggs,  D.  H.,  and  Simon,  J.  R., "Differential Effects of Noise on Tasks  of
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56.   Glass,  0.  C.,  and Singer,  J.  E.,  Urban Stress  Experiments  on  Noise and
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57.   Wilkinson, R.  T., "Some  Factors  Influencing  the Effects  of Environmental
     Stressors  Upon Performance,"  Psychological Bulletin,  Vol. 72,  (1969),  pp
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58.   Blake,  M.  J.  F.,  "Temperamenc  and Time of Day,"  in Biological Rhythms and
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59.   Davies, D. R., and Hockey, G.  R. J., "The Effects of Noise  and Doubling the
     Signal   Frequency   on   Individual  Differences   in   Visual   Vigilance
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60.   Discipio,  W. J.,  "Psychomotor  Performance as  a Function  of White Noise and
     Personality Variables," Perceptual and Motor Skills, Vol. 33,  (1971), p. 82.

61.   Broadbent, D.  F.,  Decision  and Stress,  London:   Academic Press, (1971).

62.   Kahneman,  D., Attention and Effort,  Englewood  Cliffs,  New Jersey:  Prentice
     Hall, (1973).

63.   "Industrial Noise and Worker  Medical,  Attendance  and Accident  Records,"
     U.S.  Department  of Health,  Education, and Welfare, Public Health Service,
     and  the National Institute for Occupational  Safety and Health, (June 1972).

64.   U.S.   Environmental  Protection  Agency,  Office  of   Noise Abatement  and
     Control,  "Some Considerations  in Choosing  an Occupational Noise Exposure
     Regulation,"  (February 1976).

65.   Bronzaft,  A., _McCarthy, D.,  "The Effect  of Elevated Train  Noise on  Reading
     Ability,"  Environment  and  Behavior,  Vol.  7,  No.  4,  (December  1975), pp.
     517-527.

66.   Cohen,   S.,  Glass,   D.,  and  Singer,  J.,  "Apartment   Noise,  Auditory
     Discrimination,  and  Reading Ability in Children," Journal of Experimental
     Social  Psychology, Vol.  9,  (1973),  pp.  407-^22.

67.   Griefahn,  B.,  and Muzet,  A.,  "Noise-Induced  Slesp Disturbances  and Thair
     Effects on Health,"  Institut Feur Arbeits -und Sozialmedizin, Universitaet
     Mainz,  West Germany  and  Centre d'Etudes  Bioclimatiques du  CNRS, France,

68.   Lukas,  J.  S.,  "Measures  of  Noise  Level:    Their  Relative Accuracy  in
     Predicting Objective  and  Subjective  Responses  to  Noise During  Sleep,"
     Washington, D.C.:   U.S.  Environmental Protection  Agency, 600/1-77-010,
     (February 1977).
                                        11-5

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69.   Lukas, J.  S.,  Dobbs,  M.  E. ,  "Effects of Aircraft  Noise en the  Sleep  of
     Women," National Aeronautics and Space Admiaistration, Report No.  CR  2041.

70.   Dobbs, M. E., "Behavioral Responses to Auditory SLirav.lation During Sleep,"
     Journal of Sound and Vibration-, Vol. 20,  (1972), pp. 467-476.

71.   Williams,  H.  L.  and  Williams,  C.  L.,   "Nocturral  EEC  Profiles  and
     Performance," Psychophysiol, Vol. 3, (1966), pp. 16-+-175.

72.   Grandjean,  E.  et  al.,  "A  Survey  on Aircraft  Moise  in  Switzerland,"  in
     Proceeding  of   the  International Congress  on  Noise  as  a  Public Health
     Problem,  550/973-008,  (1973), pp. 615-660.

73.   Scharf,  B.,  et  al., U.S. Environmental  Protection  Agency,  "Comparison  of
     Various Methods  for Predicting the Loudness and Acceptability  of Noise,"
     550/9-77-101, (August 1977).

74.   National Academy of Science - National Regulatory Ccmmissian, Committee  on
     Hearing,  Bioacoustics, and Biomechanics,  "Proposed Dama§^  - Risk Criterion
     for Impulse Noise (gun fire)."  Report  of  Working Group 57, Washington, D .C.
     (1968).

75.   McLean, E. K.,  and Tarnopolsky,  .-». ,  "Noise,  Discomfort, and Mental Health,"
     Psychological Medicine,  (Augusr 1977), pp.   19-51.

76.   Borksy,  P.,  "Review  of  Community  Response  to  Noise,"  contained  in
     proceedings  of  3rd  International  Congress  on  Noise  as  a  Public Health
     Hazard,  American  Speech  Language  Hearing Assoc.,  Report  10,  (1980), pp.
     452-474.
77.   Matthews,  X. E.,  and  Canr.on,  L.  K.,  "Environmental  Noise  Level   as  a
     Determinant  of  Helping  Behavior,"  Journal   of  Personality  and Social
     Psychology, (1975), pp.  571-577.

78.   Sherrod,  D. R. ,  and Downs, R. , "Env' ronmental Detatainanta of  Altruism:  the
     Effect of Stimulus Overload and Perceived Centre;  on Helping,"  Journal  of
     Experimental Social Psychology, Vol. 10,  (1974), pp. 468-479.

79.   Geen, R.  G., and Powers, P. C., "Shock and Noise as Instigating Stimuli  in
     Human Aggression," Psychological Reports, Vol.  28, (1971), pp. 983-985.

80.   Schultz,  T. J.,  "Synthesis of Social Surveys  on Noise Annoyance," Journal of
     the Acoustical Society of America, Vol.  64,  No. 2, (August 1973),  pp. 377-
     405.

81.   Committee  on Hearing,  Bioacoustics,  and   Biomechanics,   "Guidelines  for
     Preparing  Environmental  Impact  Statements  on  Noise,"  Report  of Working
     Group No. 69, National Academy of Sciences,  (1977).

82.   U.S.  Environmental  Protection  Agency,  "The  Urban  Noise  Survey," 550/9-77-
     100,  (April 1977).
                                       11-6

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83.  Goldstein,  J.,  "Assessing  Che  Impact  of  Transportation  Noises    Human
     Response Measures,"  in Proceedings of  the 1977 National Conference on Noise
     Control Engineering,  (ed.),  G.  C.  Haling,, NASA  Langley  Research  Center,
     Hampton, Virginia, (October  1977),  pp. 79-98.

84.  U.S. Department  of  Health,   Educaf.ion and  Welfare,  l:Fifth Report  of  the
     Director of  the National Heart, Lung,  and Blood Institute," DHEW Publication
     No. NIH-78-1415,  (February 1978).

85.  Jones,  F. N.,  and  Tauscher, J., "Residence Under an Airport Landing Pattern
     as  a  factor  in  Teratism,"  Archives  of Environmental  Health,  (January-
     February 1978),  pp.  10-11.

86.  Cohen,   Alexander,  "Industrial Noise  and  Medical,  Absence, and  Accident
     Record   Data on  Exposed  Workers,"  in  Proceedings  of  the  International
     Congress on  Noise  as a Public Health Problem, Dubrovnik, Yugoslavia, May 13-
     18, 1973, Washington,  D.C.:   U.S. Environmental Protection Agency,  550/9-
     73-008, (1973),  pp.  441-453.

87.  Webster,- J. C.,   "Effects  of Noise  on  Speech Intelligibility,"  in Pro-
     ceedings of  the  Conference on Noise As a Public Health Hazard,  (1969),  pp.
     49-73.

88.  Lukas,  J.  "Noise and  Sleep:  A  Literature Review and a Proposed Criteria
     for Assessing  Effect," in Handbook  of  Noise Assessment,  ed. Darly N.  May,
     Van Nostrand Reinhold  Company:New York,  (1978),  pp. 31?-334.

89.  Thiessen, G. J.,  "Effects of Noise from Passing Trucks  on Sleep,"   Report
     Ql, presented  at  77th  meeting  of  the Acoustical  Society  of  America,
     Philadelphia,  (April 1969).

90.  Abey-Wickrania,  I., a'Brook,  M. F,, Gattoni, F. E. G.,  &  Herridge,  C.   F.
     "Mental Hospital  Admissions  and Aircraft Noise," Lancet, (1969),  pp. 1275-
     1277.
91.  ANSI,  American National  Standards Institute, "Methods  for  the  Calculation
     of the  Articulation  Index" ANSI S3.5-1969.

92.  ANSI,  American National Standards Institute, "Rating Noise with Respect to
     Speech  Interference" ANSI S3.14-1977.

93.  Horonjeff,  R.  D.,  and   Teffeteller,  S.  R.,   "Sleep  Interference  from
     Intermittent and  Continuous  Noise Exposure," presented at  the  98th  Meeting
     of  the  Acoustical Society of America, Salt Lake  City,  Utah (November  27,
     1969).

94.  Horonjeff,  R.  D., et  al.,   "Sleep Interference   from 'Low  Level  Sounds",
     presented at  the  96th  Meeting  of  the Acoustical  Society  of  America,
     Honolulu, Hawaii  (November 30,  1978).

95.  Royster, L.  H., J.  D.  Royster,  and  W. G.  Thomas,  "Representative  Hearing
     Levels   by   Race  and  Sex in  North  Carolina   Industry",  Journal  of  the
     Acoustical Society of  America.  Vol. 68,  No. 2,  (August 1980).
                                       11-7

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 96.   Cohen,  S.,  Krintz,  D. S. ,  Evans,  G.  W.  and  D.  Stokols. "Community Noi?e and
      Children: Cognitive Motivational  and Physiological  Effects."   In Tobias, J.
      V.,   Jansen,  G.,   and  Ward,  W.   D.  (Eds.).    Proceedings  of the  Third
      International Congress on  Noise as a Public Health  Problem, ASHA Report 10,
      (April  1980).

 97.   Meecham, W.  C.,  Shaw, N.   "Effects of Jet Noise on Mortality Rates," British
      Journal of  Audiology, Vol. 13, (1979), pp. 77-80.

 98.   Kryter, K.  D.,  Pazo, F.    "Effects  of  Noise  on Some  Auccnomic  System
      Activities," Journal ot the Acoustical Scoiety of America, Vol. 67, (1980),
      pp.  2036-2044.

 99.   Dept. of Labor, OSHA.   "Occupational Noise Exposure;  Hearing Conservation
      Amendment," Jan. 16, 1981.

100.   Welch,  B.  L.  Extra-auditory Health  Effects of Industrial  Noise:  Survey of
      Foreign Liteature,  June 1979.

101.   Knipschild,  P.   "Medical  Effects of Aircraft Noise:   Drug  Survey"   Int.
      Arch. Occup. Envir.  Health.  Vol. 40  (1977).

102.   Cantrell,  R. W.  "Prolonged  Exposure to Intermittent  Noise:   Audiometric,
      Biochemical,  Motor,  Psychological,   a-.id  Sleep   Effects"    Laryngoscope
      Supplement  I Vol.  84, No.  10, pt. 2,  (Oct. 1974).

103.   Ising,  M.  et  al.   "Study  on  the Quantification  of Risk for  the Heart and
      Circulatory System Associated with Noise Workers."   Institute  for Water and
      Air Hygiene of the BGA, Berlin (1979).

104.   Karsdorf, G. and Klappach, H.  "The  Influence  of Traffic Noise on the Health
      and Performance of Secondary School  Students   in  a  Large City.1' Zeitschrift
      fur die Gesamta Hygiene,  (1968).

105.   Manninen,  0. and Aro S.    "Noise-induced  Hearing Loss and Blood i'ressure.
      Int'l Archives of  Occup. and Envir.  Health, Vol. 42,  (1979).

106.   Peterson,  E. et al.  "Noise Raises Blood Pressure Without Impairing Auditory
      Sensitivity"  Science, Vol. 211,  No. 4489, (Mar  27, 1981).
                                     11-8

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INDEX
AAOO (American Academy of Ophthalmology and Otolaryngology)
     Hearing impairment compensation formula, 2-30
ABC Network
     Harris survey, 1-2
AMA (American Medical Association)
     Hearing impairment compensation formula, 2-31
Absenteeism—see Workplace


Accidents—see Safety
Acoustic Reflex
     Defined, 2-10
Adrenalin
     Part of stress syndrome, 3-1
Aftereffects
     On performance, 5-2, 5-4
Age
     Hearing differences, 2-4
     Effect on hearing loss, 2-15 to 2-16
Air Conduction
     Testing, 2-4, 2-6
Aircraft Noise
     As souice of neighborhood dissatisfaction,  1-1
     Population exposed to, 1-1 to 1-4
     Relation to cardiovascular problems, 3-4
     Possible fetal effects, 3-9
     Relation to mental illness, 7-1
     Relation to mortality rates, 3-9
                                12-1

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Airport Noise—see Aircraft Noise
Annoyance
     Neighborhood dissatisfaction, 1-1, 8-1
     Population annoyed, 1-1 to 1-2
     Population severely annoyed, 1-2
     As a function of Ldn, 10-
     Survey results, 8-1, 8-4 to 8-7
     Effects of noise quality, 7-4
     Means, 8-1
     Predictors, 8-2, 8-4 to 8-6
     Relation to socioeconomic status, 8-8
     As psychological response, 7-4
     From sleep disturbance, 6-1, 6-7
     Schultz curve, 8-5
     Special populations, 7-4
     As index of community reaction, 8-3
Annual Housing Survey
     Findings, 1-1, 8-1
Antisocial Behavior
     As stress effect, 7-5
Arousal Response—see also Startle Reflex
     Defined, 3-1
Articulation index—see Communication Interferer.ee
Attitudes—see also Annual Housing Survey
                    Urban Noise
     As a function of L. , 10-1 to 10-6
                       an
Audiogram—see also Hearing, Measurement
     Sample, 2-5
     OSHA requirements, 2-27 to 2-28
     Types of uses, 2-29
Audiometry—see Audiogram
                Hearing Measurements
Auricle—see Ear Function
                            12-2

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Automobile Noise—see Traffic Noise
Autonomic Nervous System
     In physiological response, 5-2
Awakening—see Sleep Disturbance


Babies—see Fetus


Balance—see Vertigo
Benefits—see also Compensation
     Of regulations, 9-1 to 9-2
Birth Defects
     Possible link with noise, 3-1, 3-10
     Effect en hearing, 2-6
Birth Weights
     Low birth weights, 3-1, 3-S
Budgets—see Costs
Blood Pressure
     Arousal response, 3-1
     Vasoconstriction, 3-2
     Hypertension, 3-1 to 3-6
     In laboratory animals, 3-5
     Pressure changes as stress effect, 3-4
Bone Conduction
     Thresholds, 2-4
     Testing, 2-6
CHABA
     Guidelines, 2-14, 8-6
Cardiovascular Disease
     As stress effect, 3-1
     Relationship to noise, 3-3 to 3-5
                             12-3

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Car Noise—see Traffic Noise


Census Bureau—see Annual Housing Survey


Center for Disease Control
     Fetal birth weight studies, 3-10
Children
     With hearing loss, 2-8
     Effects during sleep, 6-6
     Physiological stress effects on, 3-5
     Performance interference, 5-5
Cholesterol
     Relation r.o noise, 3-3
City Noise—see Urban Noise
               i

Cleft Palates—s°e Birth Defects


Cochlea—see Ear Function
Colitis—see also Digestive Disorders
     As stress effect, 3-1, 3-7
Conmunication Interference
     In general, Chapter 4
     As a function of Ldn,  10-1
     Resulting from hearing loss, 2-19 to 2-20
     Indirct effects, 4-1
     Effects on social interaction, 4-1
     Effects on safety, 4-1
     Effect of speech quality, 4-2
     Factors of extent, 4-2
     Criteria, 4-4 to 4-6
     Articulation index, 4-3
     Effects of temporal quality, 4-2 to 4-3
     Speech interference level, 4-3
     Best weighting scale, 4-3
     Protective levels, 4-4
     Intelligibility, 4-3
     Relating to community response, 8-1
     Effects on children, 4-8 to 4-9
                           12-4

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Communication Interference (Continued)
     Effect of age, 4-8
     From hearing loss, 4-8
Community Response
     In general, Chapter 8
     As a function of Ldn, 10-1 to 10-6, 9-4
     Relating to activity interfernece, 8-1, 8-7
     Neighborhood dissatisfaction, 1-1, 8-1, 8-9
     Number of people at various exposure  levels,  1-2  to  1-4
     Opposed to individual response, 8-4
     Synthesized data, 8-4 to 8-6
     Relation to complaints, 8-4, 8-8
     Comparison of Levels Document and prior survey data,  8-4  to  8-6
     Relation to population density, 8-8 to 8-9
     Relation to contextual factors, 8-8 to 8-9
     Index of annoyance, 8-3
     Socioeconomic factors, 8-8
     How measured, 8-2
     Criteria, 8-4 to 8-6
Compensation
     Hearing impairment formulas, 2-30 to 2-31
     State policies, 2-29 to 2-31
     Why paid, 2-29
     Use of audiograms, 2-29
     Legal terms, 2-30
Compensation Formulas—see NIOSH
Complaints—see also Community Response
     At various noise levels, 8-3 to 8-6
     Predictive value, 8-2
Conductive Hearing Loss
     Defined, 2-5
     How determined, 2-6
     Causes, 2-5
Congenital Problems—see Birth Defeccs
                         Fetus
Contextual Factors—see also Psychologicr.l Response
     Relation to community reaction, 8-8
                            12-5

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Controllability
     Effect on response, 5-2
Coping Behavior
     From excessive exposure, 7-5
Coronary Disease—see Cardiovascular Disease


Cortisol
     Increases in levels associated with noise, 3-6
Costs
     Of cardiovascular disease, 3-4
     Of work disruption,  5-5
Criteria
     For nonauditory effects, 3-3
     Hearing  loss,  2-21
     Speech interference, 4-4 to 4-6
     Sleep disruption, 6-3 to 6-4
     Steady state noise,  2-24
     For impulse noise, 2-14
     Summary  tables, as a function of Ldn,  10-1 to 10-5
Daily Noise Exposure
     Hypothetical,  1-5  to  1-6
Digestive Disorders—see  also  specific  type
     From noise-induced stress,  3-1  to  3-2,  3-7
Disability
     Defined  for  compensation,  2-30
Drugs—see Toxic  Substances
Ear Function
     Description,  2-1  to  2-2
     Testing,  2-4  to 2-6
     Disruptive diseases,  2-6  to  2-7
     Organ of  Corti, 2-13
                            12-6

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EEC Changes
     Noise-related, 6-2
Elderly
     With hearing loss, 2-8
     Effects during sleep, 6-6
     Presbycusis, 2-15 to 2-16
Endocrine Disorders
     As stress pffect, 3-7
Education—see Learning
Equal Energy Hypothesis
     Defined, 2-13
     Accuracy, 2-22
Equal Loudness Contour
     Displayed, 7-4
£qual Temporary Effect Hypothesis
     Defined, 2-12
Equivalent Noise Impact (ENI)—Level-Weighted Population  (LWP)
Exposure (to Noise)—see also Residential Exposure
                              Occupational Noise
                              Urban Noise
     Long-term nonauditory effects, 3-3
     Short-term nonauditory effects, 3-2
Fatigue
     As stress effect, 3-7, 7-1
     From high-intensity noise, 5-2
     From sleep disruption, 6-1
Fetus
     Hearing damage, 2-6
     Physiological effects, 3-1, 3-8
 'Flight or Flight Syndrome"—see Arousal Response
                           12-7

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Gallup  Poll
     Results,  1-2
Gastrointestinal  Problems—see Digestive Disorders
Harris Survey
     Results,  1-2
Handicap
     Defined  for  compensation,  2-30
Headaches
     Noise related,  3-7
Hearing Conservation—see also Hearing Loss
                               Hearing protectors
                               Audiograms
     Methods, 2-24  to 2-28
Hearing Loss—see also hearing Loss, Types
     In general, Chapter  2
     Population at risk,  1-5
     Measurement of,  2-6
     Relation to exposure,  2-9
     Physiological basis, 2-11
     Effects, 2-17 to 2-20
     Compensation formulas, 2-30 to 2-31
     Causes, 2-6 to 2-7
     Susceptibility,  2-9, 2-11
     From rock music, 2-18
     Protective levels, 2-21
     Protective emasures, 2-24 to 2-28
     Due to aging, 2-16
     Compensation, 2-29 to  2-31
Hearing Loss Claims—see Compensation
Hearing Loss, Types—see specific type:
     Conductive
     Sensori-neui'*!
     Presbycusis
     Sociocusis
Hearing Mechanism—see Ear Function


                            12-8

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Hearing, Measurement—see also Audiogram
     Method, 2-4, 2-29
     Of hearing loss, 2-6

Hearing, Normal
     Based on sex, 2-3
     Based on race, 2-4
     Based on age, 2-4
     Range, 2-1
Hearing Protectors
     Types, 2-27 to 2-28
     Attenuation characteristics, 2-28
Hearing Tests—-see Hearing, heasurement


Heart Problems—see Cardiovascular Disease
Helping Behavior
     Effects from excessive exposure, 7-5
High Frequency Noise
     Effects on performance, 5-2
     Effects on subjective response, 7-4
Household Noise
     Typical exposure, 1-5
HUD
     Annual Housing Surveys, 1-1
Hypertension
     As a stress effect, 3-1 to 3-6
     Monkeys, 3-4
Hypotension
     As a stress effect, 3-7
Immunological Resistance
     Reduction from stress, 3-1
                            12-9

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Impairment
     Defined for compensation, 2-30


Impedar.ce
     Friction, 2-2
Impulse Noise
     Effects, 2-13
     Effect on speech interference, 4-2
     Criteria, 2-14
Individual Response—see Psychological Response
Indoor Noise
     Compared to outdoor levels, 1-6
     Criteria, 4-4 to 4-5
Industrial Noise—see Occupational Noise


Infants—see Fetus
Information Content
     Effect on sleep disturbance, 6-5
     Effect on work performance, 5-3
Information Gathering—see Learning
                           Communeiation Interference
                           Performance Interference
Insomia
     Noise related, 3-3
Interior Noise
     Relation to outdoor noise, 1-2
Intensity—see also Loudness
     Relation to subjective response, 7-2
Intermittency
     Effect on performance, 5-2
                          12-10

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Intermittency (Continued)
     Effect on speech interference, 4-2
     Effect on subjective response, 7-2
     Correction factor, 2-22
Irritability
     As stress effect, 2-5, 7-1
     In noisy work environments, 5-5
Kryter, Karl
     Studies, 3-8
Learning
     Effects from speech interference, 4-8 to 4-9
     Disruption, 5-3, 5-5
Legislation—see Walsh-Healey Public Contracts Act
                 OSHA
Levels—see Recommended Levels
Level-Weighted Population
     Defined, 9-1 to 9-2
Loudnsss
     Effect on performance, 5-2
     Effect on sleep, 6-2 to 6-6
     Effect on threshold shift, 2-9
     Of rock music, 2-18
     Effect on subjective response, 7-2,  7-4
     Effect from recruitment, 2-19
     Effect on communication, 4-1
Masking—see Communication Interference
Mental Effects—see Psychological Effects
                    Physhological Response
Mecham, W.C.
     Studies
Mental Illness
     Relation to excessive noise, 7-1
                             12-11

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Metabolic Disorders—see Physiolgoical Effects


Migraines—see Headaches


Modifications—see Strategies, Control
Monkeys
     Blood pressure study,  3-5
Mortality Rates
     Effects  from noise,  3-9
NIOSH  (National  Institute of Occupational Safety and Health)
     Hearing  impairment compensation  formulas, 2-31
     Hearing  loss  formula,  2-31
National Health Examination  Survey
     Of tinnitus,  2-20
National Institute  of Occupational  Safety  and Health—see NIOSH
National League of  Cities
     Gallup  poll,  1-2
National Noise  Problem
      In general,  Chapter  1
      People  exposed,  1-1  to  1-5
      Typical exposures,  1-5  to  1-6
      Workers, exposed,  1-4
Nausea
     From high-intensity  noise,  5-2
Neighborhoods—see  also Annoyance
                        Urban  Noise
                        Annual Housing  Survey
     Community response surveys,  1-1  to 1-2, 8-1  to  8-9
     Dissatisfaction,  9-1
     Satisfaction as  a function of L.  ,  10-1 to  10-6
                         12-12

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Neuroticism
     As stress effect, 3-5
Newborn—see Fetus
Nonauditory Effects—see also Physiological Effects
                              Stress
     In general, Chapter 3
     Physiological changes, 3-1
     Vasoconstriction, 3-2
     From short-term exposure, 3-2
     From long-term exposure, 3-3
     Criteria, 3-3
     Cardiovascular problems, 3-1, 3-3 to 3-7
     Blood pressure^ 3-1, 3-3 to 3-6
     Stress effects, 3-4 to 3.-6
     Toxic substances, 3-1, 3-8
     Fetus, 3-1, 3-10
     During sleep, 6-2
     On workers, 3-7
     Differences in scientific opinion, 3-8
OSHA
     Requirements, 2-14, 2-27 to 2-28
Occupational Safety and Health Administration—see OSHA
Occupational Noise
     Compensation for hearing impariment,  2-29  to  2-31
     Number of workers at risk, 1-5
     Regulations, 2-14, 2-24
     OSHA requirements, 2-27 to 2-28
     Protective levels, 2-14, 2-21, 2-26
     Impulsive noise, 2-14
     Performance effects, 5-5
     Societal costs, 5-5
Old People—see Elderly


Ossicular Chain—see Ear Function
                         12-13

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Ototocix Drugs—see Toxic Substances
Performance Interference
     In general, Chapter 5
     Exposure factors, 5-1
     Exposure effects, 5-1 to 5-5
     Detrimental levels, 5-2
     Detrimental noise qualities, 5-2 to 5-3
     Cumulative effects, 5-4
     From  industrial noise, 5-5
     Aftereffects,  5-2Performance Interference (Continued)
     Societal costs, 5-5
     Fatigue  from noise related  stress, 5-5, 7-1
     Affected tasks, 5-3
     Individual variables, 5-3
     Of  learning, 5-3
     Positive effects,  5-1, 5-4
     After effects,  5-4
     On  children, 5-4
 Personal  Factors
      In subjective  response,  7-2,  7-5
      In community response,  8-8
 Peterson,  Ernest
      Blood pressure,  3-5
 Phon
      Defined,  7-3


 Physiological Effects—see also Nonauditory Effects
      Arousal response, 3-1
      Of high-intensity noise, 5-2
      During sleep, 6-1 to 6-2
      Autonomic nervous system, 3-2
 Population Density
      As predictor of annoyance, 8-8 to 8-9
 Predictability
      Effect on performance, 5-2
 Pregnant Women—see Fetus
                           12-14

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Presbycusis
     Defined, 2-15
     Progression, 2-15 to 2-16
Primates—see Monkeys
Psychological Effects
     From industrial noise, 5-2
     From high levels of noise, 7-1
Psychological Response
     In general, Chapter 2
     To high-intensity noise, 5-2
     To excessive noise, 7-1
     Subjective response to noise quality, 7-2
     Contextual factors, 7-2
     Personal factors, 7--2
     Best weighting scale, 7-2
     Annoying noises, 7-4
     Of special populations, 7-4
     Role of personality, 7-2
     Coping behavior, 7-5
     Antisocial behavior, 7-5
     Use of sones, 7-3
     Use of phons, 7-3
Public Health Survey
     On hearing loss, 2-7 to 2-8
Public Opinion—see Annual Housing Survey
                    Community Response
                    Surveys
                    Urban Noise

Race
     Hearing differences, 2-4
Rapid Eye Movement (REM)
     Disruption, 6-6
Recommended Levels
     Levels Document identified levels, 2-21
     Validity of basis, 2-22
     Appropriate for speech, 4-4
                        12-15

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Recruitment:
     Defined, 2-19
Regulations
     Occupational noise, 2-14, 2-24, 2-26 to 2-27
     Health and Welfare analysis, 9-1 to 9-2
REM—see Rapid Eye Movement
Residential  Exposure—see also Household Noise
      Survey  results,  1-1  to  1-4
      Near  airports, 7-1
      In urban  areas,  8-1  to  8-8
Rock Music
     Effects,  2-18
     Levels,  2-18
 Safety
      Field study,  3-8
      Effects  from communeiation interference,  6-1
      Effects  from stress,  7-5
 Schools—see Learning
 Schultz Curve
      Displayed,  8-5
 Senior Citizens—see Elderly
 Sensori-Neural Hearing Loss
      Defined,  2-6
      Causes,  2-7
 Sex
      Hearing differences, 2-3
      Effect on sleep disruption, 6-5
 Shaw, W.
      Studies, 3-9
                             12-16

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Sleep Disturbance
     In general, Chapter 6
     Effects,  6-1
     Awareness, 6-1
     Indirect  effects, 6-1
     Disruptive noise levels, 6-2
     Physiological effects, 6-3
     Probability of disruption, 6-3
     Variance  with noise level, 6-5 to 6-6
     Probability of awakening, 6-5
     Effects of sound quality, 6-2, 6-6
     Effects of age and sex, 6-6
     Effects of sleep duration, 6-5
     Effects of noise duration, 6-2
     Effects of sleep deprivation, 6-7
     Effects of time of night, 6-3
     Survey data, 6-6
     Stages of sleep, 6-3
     Long-term effects, 6-7
     Relating  to community response, 8-1
     Criteria, 6-4 to 6-5
Social Interaction
     Effects from communciation interference, 4-1
     Effects from excessive exposure, 7-5 to 7-6
     Effects from hearing loss, 2-2C
Sociocusis
     Defined, 2-15
     Evidence of occurance, 2-17
Socioeconomic Status
     Effect on psychological response, 7-2
     Relation to annoyance, 8-8
Sone
     Defined, 7-3
Special Populations—see also Fetus
                              Children
                              Age
                              Sex
                              Workers
                              Elderly
     Noise sensitive, 7-4
     Affected by masking, 4-8 to 4-9
                          12-17

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Spectral Characteristics
     Effect on performance, 5-23
     Effect on subjective response, 7-2


Speech Interference—see Communication Interference


Standards—see Regulations


Startle Reflex—see Arousal Response
Statistics
     Residential exposure, 1-1 to 1-5, 8-7 to 8-9
     Societal costs, 5-5
     Hearing loss extent, 2-7 to 2-8
Strategies, Control
     Noise reduction, 2-24 to 2-26
     Source modification, 2-25
     Path alteration, 2-25
Stress, Mental—see also Annoyance
     From excessive noise, 3-5, 7-1
Stress, Physical
     As noise effect, 3-1 to 3-10
     From industrial noise, 5-5
Subjective Response—see Psychological Effects
                         Psychological Response
Surveys—see also Urban Noise
                  Annual Housing Survey
     On sleep disruption, 6-7
     On community response, 8-1 to 8-8
     On subjective response, 7-5
Susceptibility
     To hearing loss, 2-9 to 2-10
     Etfect os ex, 2-11
     Testing, 2-29
     Of children, 5-5
     To infection or toxic substances, 3-1
                          12-13

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Svnergism
     with toxic substances, 2-10, 3-8
Tasks, Noise Sensitive
     Types, 5-3
Terminology—see Acoustic Terminology
Tinnitus
     Defined, 2-20
     Extent. 2-20
Threshold of Audibility
     Normal hearing, 2-2
Threshold of Pain
     Level, 2-3
Threshold Shifts, Noise Induced
     Permanent, 2-7, 2-9, 2-23 to 2-24
     Temporary, 2-12 to 2-13, 2-18
     Predictions, 2-12 to 2-13
     From loud music, 2-18
     Steady-state exposure criterion, 2-24
     Relation to exposure levels, 2-7
     From continuous noise,  2-24
Toxic Substances
     Hearing effects, 2-7,  2-10
     Synergistic effects,  3-6
     Susceptibility,  3-1
Traffic Noise—see also  Specific  Vehicle  Types
     As source of neighborhood dissatisfaction,  1-1  to 1-2
     Population exposed  to,  1-1  to  1-4
     Relation to cardiovascular  problems,  3-4
Traumatic Hearing Loss
     Defined, 2-6
                          12-19

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Typical Noise Exposures
     In Schorl study, 1-4
     Hypotheticsl, 1-5 to 1-6
Ulcers--see also Digestive Disorders
     A3 stress effect, 3-1, 3-5
Urban Noise
     Sources,  1-1 to 1-4
     Population exposed, 1-1 to 1-4
     Survey results, 1-1 to 1-2, .8-7 to 8-9
     Survey conclusions, 10-9
Urban Noise Survey—see Urban Noise
Undesirable Neighborhood Conditions
     Noise, 1-1 to 1-2
Vasoconstriction
     In startle (arousal response), 3-1
     Of uterine blood vessels, 3-10
     During sleep, 6-2
     As stress effect, 3-2
Vehicle Noise—see Traffice Noise


Vestibular Problems—see Vertigo
Vertigo
     From high-intensity noise, 5-2
Vigilance Tastes
     Disruption factors, 4-2,  5-3
Walsh-Healy Public Contracts Act
     Permissible exposure  levels,  2-27
Weighting Schemes
     A-weighting, 4-3
     For measuring subjective response,  7-2  to  7-3
     Stevens' Mark VII and VIII,  7-2
     Zwicker's procedures, 7-2  to  7-3
                          12-20

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Womb—see Fetus


Workers—see Occupational Noise


Work Performance—see Performance Interference
Workplace
     Absenteeism, 3-8
     Cost of exposure, 5-5
                         12-21

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