550/9-74-003-A
CONTROL OF SNOWMOBILE NOISE
VOLUME I
TECHNOLOGY AND COST INFORMATION
JUNE \m
U.S. Environmental Protection Agency
Washington, D.C. 20460
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Document is available to the public through the National Technical
Information Service, Springfield, Virginia 22151
Document is available in limited quantities through the Environmental
Protection Agency, Office of Noise Abatement and Control, Arlington,
Virginia 20460
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550/9-74-003-A
CONTROL OF SNOWMOBILE NOISE
VOLUME I
TECHNOLOGY AND COST INFORMATION
JUNE 1974
Prepared For:
U.S. Environmental Protection Agency
Office of Noise Abatement and Control
Under Contract No. 68-01-1537
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AC KN OWLE DG MEN TS
The authors would like to thank the many snowmobile firms who contributed their
time in supplying data for this study. In particular, we appreciate the efforts of Mr.
James Lamont of Polaris, Mr. Nick Hirsch and Mr. Larry Eriksson of Harley-Davidson,
Mr. Howard Larson and Mr. Dick Lincoln of OMC, Mr. Roger Worth, Mr. Gus
Englert and Mr. Roger Anderson of Arctic, Mr. Lowell Haas of Scorpion, Mr. George
Gowing of Bombardier, Mr. Nick Shiokawa and Mr. Keith Emi of Yamaha and Mr.
Martin Berk of John Deere. We are grateful to Mr. Theodore Breton of the U.S.
Environmental Protection Agency for providing many helpful comments and suggestions
during this study, to Mr. Jasbinder Singh of the International Research and Technology
Corporation for his help in developing the format for presentation of component cost
data and to Mr. John Nesbitt of the International Snowmobile Industry Association
for commenting on the draft report.
Many staff members of Wyle Research were very helpful during this project. Mr.
Louis Sutherland and Mr. Ed Thurston contributed many useful comments on the technical
contents of the report. Dr. Herbert T. Spiro, in his role as consulting economist, pro-
vided the section on industry structure and contributed many suggestions concerning
interpretation of the data. We especially wish to thank Mr. Robert Johnson for doing
the graphics and the art work.
ii
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TABLE OF CONTENTS
Page
1. INTRODUCTION 1
2. STUDY APPROACH 2
3. THE SNOWMOBILE INDUSTRY 4
Industry Grouping 4
4. SNOWMOBILE CONSTRUCTION AND NOISE CHARACTERISTICS . 6
Introduction 6
Measurement Procedures 7
A-We5ghted Noise Levels and Spectra 10
Operator Noise Exposure 17
Noise Sources 19
5. SELECTED NOISE LEVELS 22
o. NOISE REDUCTION TECHNIQUES AND COSTS 25
Noise Reduction from Subsources 27
Achievement of the Selected Noise Levels Through Application
of Noise Reduction Techniques 31
Weight Increases Due to Noise Reduction 36
Lead Time Requirements 39
7. RECOMMENDATIONS FOR FURTHER WORK 40
REFERENCES 41
in
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APPENDIX A
APPENDIX B
APPENDIX C
APPENDIX D
TABLE OF CONTENTS (Continued)
SNOWMOBILE MANUFACTURERS CONTACTED
FOR THIS STUDY
DESIGN FEATURES, RETAIL COSTS AND MEASURED
NOISE LEVELS FOR 1973 SNOWMOBILE MODELS
SAE RECOMMENDED PRACTICE FOR EXTERIOR
SOUND LEVEL FOR SNOWMOBILES . . .
STATE SNOWMOBILE NOISE LEGISLATION: 1972
Page
. A-l
B-l
. C-l
. D-l
IV
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LIST OF TABLES
Number Page
1 Grouping of Snowmobile Firms 5
2 Maximum Noise Levels at Operator's Ear and at 50 Feet 19
3 Selected Noise Levels for Potential Noise Regulation of 24
Snowmobiles
4 Estimated Per-Machine Manufacturing Cost Increases for 32
Noise Reduction in Snowmobiles
5 Summary of Estimated Noise Reduction Costs for Snowmobiles 36
6 Estimated Snowmobile Weight Increase Due to Noise Reduction 38
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LIST OF FIGURES
Number Page
1 Typical Snowmobile Configuration 6
2 Snowmobile Pass-by Noise Versus Speed — 1973 Model 8
Vehicles
3 Relation Between Noise Levels Measured on Packed Snow 9
Snow and 3 Inches of Grass
4 Noise Levels of 1973 Model Snowmobiles as a Function of 11
Engine Size (All Manufacturers)
5 Noise Levels of 1973 Model Snowmobiles as a Function of 13
Engine Size (Group 1 - Large Manufacturers)
6 Noise Levels of 1973 Model Snowmobiles as a Function of 14
Engine Size (Group 2 - Small Manufacturers)
7 Noise Levels of 1973 Model Snowmobiles as a Function of 15
Power/Weight Ratio
8 Noise Levels of 1973 Model Snowmobiles as a Function of 16
Retail Price
9 Typical Snowmobile Noise Spectrum 17
10 Synthesis of Representative Snowmobile Component Noise 20
Sources into an Overall A-Weighted Noise Level
11 Estimated Manufacturing Costs for Snowmobile Noise Reduction 33
as a Function of Level Obtained (Group 1 - Large Manufacturers)
12 Estimated Manufacturing Costs for Snowmobile Noise Reduction 34
as a Function of Level Obtained (Group 2 - Small Manufacturers)
13 Estimated Snowmobile Weight Increase Due to Noise Reduction 37
Equipment (Group 1 - Large Manufacturers)
14 Estimated Snowmobile Weight Increase Due to Noise Reduction 38
Equipment (Group 2 - Small Manufacturers)
VI
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1. INTRODUCTION
The snowmobile is one of the most popular recreational vehicles in the northern
United States and Canada. From a production of 10,000 units in 1963 the industry
has grown to almost 600,000 units in 1973. There are an estimated 2.3 million snow-
mobiles in use today and of these, one million are less than 3 years old. Pure recrea-
tion accounts for 98 percent of snowmobile use and the average snowmobiler spends
14 hours per week during the winter season on a machine he purchased for an average
price of $1146.
In 1971 there were 69 known snowmobile manufacturing firms in the world. At
present, 38 firms are known to make snowmobiles and the eight largest firms control
over 70 percent of the entire market. Last year the industry's estimated sales volume
was $500 million.
Due partly to its rapid growth in popularity and partly to the fact that earlier
models were very noisy (levels in excess of 100 dBA at 50 feet were not uncommon
during the 1960's), many complaints of annoyance have been registered against snow-
mobiles. In addition to the annoyance factor, there are indications that snowmobile
noise might cause permanent hearing damage to operators and passengers. Finally,
conservationists are concerned that snowmobile noise might be detrimental to wildlife
at a time when they are particularly weak and vulnerable. Many studies have been
conducted on these aspects of snowmobile noise with the result that legislation has been
introduced in many states to restrict noise levels. Manufacturers have responded to
this legislation somewhat by producing quieter snowmobiles for use today, and by
instigating research and development programs to achieve further reductions in noise
levels of future models. This report documents the costs that are expected to be
incurred by manufacturers to produce snowmobiles quieter than presently available
models.
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2. STUDY APPROACH
A feasibility study on the noise reduction of one or two snowmobile models
would result in information of limited general application because of the wide variety
of snowmobiles on the market today. Such studies have been carried out in the past
by independent research organizations and their results have been well documented
although not always well received by the industry. Prodded by recent legislation,
most manufacturers have begun research on their own. As this study progressed, a
great deal of data were made available by manufacturers, government agencies, trade
magazines and independent research groups. The scope and quality of the data was
considered sufficient to justify abandoning any in-house tests of noise reduction for
this prog ram.
A total of 38 manufacturers of snowmobiles were contacted by telephone and
by letter during the initial phase of this project. Manufacturers were asked to respond
to the following questions:
• Noise level data measured per the SAE J192 test procedure for all models
for the years 1972, 1973, and 1974.
• Cost of noise reduction techniques and materials used for 1973 and 1974
model year snowmobiles
• Cost of noise reduction techniques and materials planned for use on 1975
and 1976 model snowmobiles
• Performance changes encountered or anticipated due to noise reduction
• Weight increases encountered or anticipated due to noise reduction
• Opinions on reasonable future noise levels and test procedures
• Available operator noise levels and procedures used to measure them
• Use cycle or typical operation data
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• Subsource component1 contributions to overall noise level
• Numbers of units produced in each model designation
Market penetration data provided by manufacturers and an independent source/
together with estimates of the production of some of the smaller manufacturing firms,
indicate that the manufacturers who were asked to supply data represent approximately
97 percent of the snowmobile market. A list of all manufacturers that were contacted
is included in Appendix A to this report.
After the initial contacts were made, several representative firms were visited.
During these visits, in-depth discussions were held concerning snowmobile noise tech-
nology, feasibility of noise reduction techniques, and cost of such reduction. In addi-
tion to the questions listed above, discussions were held on snowmobile life expectancy,
the ability of smaller firms to stay in business, and specific engineering techniques
used for noise reduction. In all, personal discussions were held with engineering
representatives of seven major snowmobile firms, accounting for over 55 percent of all
units manufactured. These discussions were held at the manufacturers' facilities, at
Wyle Research, and at the International Snowmobile Industry Association 1973 Trade
Show in Toronto.
In general, snowmobile manufacturers were very cooperative in supplying infor-
mation for this project. Fourteen of the 38 manufacturers responded to our request for
data. These 14 manufacturers represent a combined market penetration of over 80 per-
cent of the snowmobile market. Many of the manufacturers who make up the remaining
20 percent of the market indicated an interest in supplying information but apparently
found it difficult to do so within the time limits imposed by the study contract.
Some of the data provided by manufacturers was considered to be of a proprietary
nature. In these cases, it was not included in this report in specific detail. In many
cases, proprietary data was generalized to facilitate its use without violating its con-
fidential nature.
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3. THE SNOWMOBILE INDUSTRY
Snowmobiles are a relatively recent, consumer oriented, leisure time product.
Only limited financial and engineering resources are required to enter the business at
this stage since the designs are still simple and consumer preferences not yet that well
established. For this reason, the industry supplying the product is still in transition,
with new firms entering the industry and older firms exiting after encountering produc-
tion, marketing or financial problems.
A profile of the industry presents, therefore, an unusual range of participation.
At- one extreme are very large manufacturing firms with diverse business interests
attempting to capitalize on their production and marketing skills and viewing snow-
mobiles as a diversification move from their other endeavors. At the other extreme
are small organizations with limited overall capabilities, yet successful in assembling
a competitive vehicle.
It is premature to anticipate the characteristics of a firm which will successfully
compete in this industry in the long run. Even present market penetration cannot be
viewed as an indicator of future market dominance. It appears clear, however, that
an engineering capability competent of meeting regulatory standards is a prerequisite
for a long term survival.
Industry Grouping
In order to test the sensitivity of survey results to the type of firm in the industry,
supplying firms were evaluated in terms of their corporate affiliation, product lines and
corporate size. Two distinct categories emerged from this analysis, each possessing a
set of internally consistent characteristics.
The first category (Group 1) encompasses very large firms with annual sales in
excess of $1 billion and medium size firms with annual sales ranging from $100 to $500
million. For the large firms, snowmobiles are most probably viewed as a potential
diversification move into the booming leisure-time market. The medium size firms
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generally have a heavy consumer orientation geared particularly to leisure-time
products. Typically these firms also manufacture and market lawn mowers, tennis
and golf equipment, camping supplies and associated products. An overriding char-
acteristic of all the firms in this group is that they possess sizable engineering and
financial resources.
The second category (Group 2) consists of smaller firms, for which snowmobiles
are the primary business activity. Their skills range from assembly operations to
limited engineering and design. They face considerable marketing problems and their
financial resources are limited. Since they do not face the involved decision and
approval processes prevalent in the other category, their strength is in their ability
to respond to consumer and regulatory demands if changes can be accomplished with
the resources they have in hand. Their annual sales are typically in the $10 to $30
million range. The two groups of manufacturers are listed in Table 1 according to
this grouping based on the information available at the time this study was made.
Table 1
Grouping of Snowmobile Firms
Group 1
(Large Manufacturers)
AMF (Harley-Davidson)
Arctic
Bombardier
Coleman
John Deere
Massey- Ferguson
Mercury
OMC
Polaris
Suzuki
Yamaha
Sno-Jet
Scorpion
(Small
Alouette
Alsport
Auto Ski
Autotechnic
Boa-Ski
Brutanza
Chaparral
Columbia - MTD
Fun Seasons
Gilson
Griswold Swinger
Herter's
Jac Trac
Group 2
Manufacturers)
Leisure Vehicles
Lori Engineering
Melvin Manufacturing
Moto-Kometic
North way
OEM
Ontario Drive and Gear
Raybon
Roll-O-Flex
Rupp
Speedway
U.S. Sports
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4. SNOWMOBILE CONSTRUCTION AND NOISE CHARACTERISTICS
Introduction
Snowmobiles are basically recreational vehicles designed for versatility, maneu-
verability and ability to go anywhere over snow. A typical snowmobile, .as shown in
Rgure 1, is usually powered by a two-cycle gasoline engine with either a single or
double piston configuration, although the rotary Wankel engine has been introduced
in some models by several manufacturers. The power from the engine is transferred
through a variable speed drive system (centrifugal clutch) to the driving track. The
track is a continuous loop of rubber or polyurethane that may be reinforced with steel
cleats for improved traction. It is normally supported on a series of spring-mounted
wheels called bogies, although in the past few years, bogie suspension systems have
been replaced with sliding rail systems or a combination of sliding rails and bogies.
Steering is accomplished by means of skis that extend through the bottom of the front
of the chassis supporting the weight of the front end. The skis are maneuvered by a
handlebar arrangement similar to that found on motorcycles. The engine is usually
mounted on the front of the chassis and covered with a cowling to form the engine
compartment. The driver sits on a padded seat covering the rear of the chassis.
windshield
handlebars
Engine
Compartment
suspension system
(Bogie Wheels or Sliders)
cooling air
louvers
Figure 1. Typical Snowmobile Configuration
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Because snowmobiles are designed to go anywhere, they must be light enough
to float over powdered snow. Heavy machines may be hazardous to ride in an area
where snow conditions change from hard-packed snow to loose powder. For this reason,
extensive use is made of aluminum and fiberglass by the manufacturer. Most popular-
sized snowmobiles weigh between 300 and 450 pounds with an average dry weight (no
fuel) of 398 pounds. Typical fuel capacity is 4 to 6 gallons. A weight design goal used
by one manufacturer to prevent sinking in loose snow is 0.5 pounds per square inch
of track surfaced For large snowmobiles, this corresponds to about 425 pounds maxi-
mum weight.
Typical top operating speed of large stock snowmobiles is about 50 miles per
hour although many racing machines are capable of much higher speeds. Normal trail
speeds are 20 to 30 miles per hour.*
Measurement Procedures
Snowmobile noise levels are most commonly measured in accordance with the
Society of Automotive Engineers (SAE) Recommended Practice J192 (See Appendix C).
Under this procedure, the snowmobile is accelerated under wide open throttle until
maximum engine speed is attained. The recording microphone is placed 50 feet from
the centerline of the vehicle path opposite a point 25 feet beyond the initial point of
maximum speed. Details of this measurement procedure are included in Appendix C.
All data in this report have been taken using the SAE J192 procedure unless otherwise
specified. Provision is made in the procedure for a 2 dB tolerance to allow for varia-
tions in test site and atmospheric conditions and differences in nominally identical
vehicles.
A standard procedure for measuring noise produced by a vehicle should provide
a method of obtaining accurate and repeatable noise level values. In addition, the
measured noise levels should correlate well with the noise produced by the vehicle
under normal operating conditions.
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One aspect of J192 that should be noted is that all noise levels measured using
this procedure are at maximum engine speed. The relation between noise level and
vehicle speed which is related to engine speed under cruise conditions is shown in
Rgure 2 for four 1973 production model snowmobiles ranging in size from 340 cc to 530 cc
All four snowmobiles represented in Figure 2 display approximately the same dependence
of noise level on vehicle speed. At typical trail speeds of 20 to 30 mph, noise levels at
50 feet range from 71 dBA to 79 dBA whereas at the maximum speed of 50 mph the levels
range from 78 dBA to 84 dBA. This variation of noise level with velocity indicates that
the levels measured according to the standard SAE test procedure are not a true Indication
of snowmobile noise levels since maximum velocity, and thus maximum engine speed, is
not a typical operating condition.
8
o
Z
o>
90
Z 85
o
£
to 80
I
^
V
75
70
65
60
55
T I
o o Vehicle A - 340 cc
A—* Vehicle B - 340 cc
O—O Vehicle C - 440 cc
°—O Vehicle D - 530 cc
I
I
10 20 30
Vehicle Cruising Speed (mph)
40
50
Source: George Cowing (See Reference 4).
Figure 2. Snowmobile Pass-By Noise Versus Speed
1973 Model Vehicles
8
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Another debatable feature of J192 is the specified test site surface. Since snow
conditions can vary considerably and at best are difficult to control, it has been
specified that the test be conducted on a grass surface. However, most manufacturing
facilities are located in the northern United States and Canada, so ironically all snow-
mobile testing must be done during warm months before it begins to snow. To alleviate
this problem of limited testing days, a new revision to J192 now permits the use of
either a grass or snow covered test site. This is, no doubt, a preferable approach from
the manufacturers' point of view. All noise level data presented in this report was
recorded in 1972 when grass was the only allowable test surface.
The variation in noise levels measured over grass and snow is shown in Figure 3.
According to one manufacturer who furnished this information, noise measured over
grass exceeds that measured over snow by approximately 7 dB. A second manufacturer
carried out a similar comparison and reported that noise measured over grass exceeds
that measured over snow by approximately 4 dB.
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The repeatability of measurements made on snow is still questionable due to
the wide variety of snow conditions that may exist. One manufacturer has found that
noise measured over softly packed snow may be as much as 5 dBA less than noise
measured over hard packed snow. As a possible solution to this problem, several
manufacturers have suggested the use of an artificial surface that could be used during
the winter.0 Such a technique would provide measurement repeatability and studies
could then be made to develop a correlation factor between measured noise and noise
produced under typical operating conditions. Obviously, the test site problem will
have to be resolved if the J192 test procedure is to become a reliable regulatory tool.
A-We?ghted Noise Levels and Spectra
Noise levels produced by snowmobiles have been declining steadily during
the last few years reflecting efforts on the part of the manufacturer to quiet his
product in response to legislation brought about by public demands for less noise.
In a recent study, the noise levels of a group of 20 snowmobiles ranging from
1967 models to 1972 models were measured/ The noise levels at 50 feet varied
from 77 dBA to 99 dBA with a mean level of 87 dBA. Legislation passed in several
states (see Appendix D) set a maximum level of 82 dBA for snowmobiles sold dur-
ing 1972 and the average level of 1973 models sold that year dropped below
82 dBA.8
Rgure 4 shows the distribution of snowmobile noise levels (measured in accord-
ance with SAE J192 test procedure on grass) for more than 200 1973 models produced
by 36 different manufacturers. The levels are given as a function of engine size
ranging from 230 cc to 650 cc with a mean engine size of 369 cc. The four most
popular sizes are 295, 340, 400, and 440 cc. Most of the snowmobiles sold during
1972 were certified between 82 dBA and 78 dBA with a mean value of 81.3 dBA. The
levels of 82 dBA and 78 dBA are the present New York State Parks and Recreation
Department noise standards for the model years 1973 and 1976 (this same New York
Standard will limit snowmobile noise to 73 dBA for the 1979 model year). All noise
10
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84
83
82
CN
^ " /• *? 5 • | Average Level
° 81
£
CO
-o
1 80
"5
< 76
75
New York State
1976 Standard
74
I I
200 300 400 500 600
Engine Displacement, cc
Source: Reference 8.
Figure 4. Noise Levels of 1973 Model Snowmobiles as a
Function of Engine Size (Data Points Represent)
Measurements made per SAE J192 Test Procedure
on a Grass Covered Test Site)
(All Manufacturers)
11
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levels in Figure 4 are absolute levels; that is, the 2 dB tolerance allowed by the SAE
J192 test procedure has not been included.
Figures 5 and 6 show the same data presented in Rgure 4 broken down by manu-
facturing group. Group 1 has a slightly lower average noise level than Group 2 but
the difference is insignificant. All data points shown on these figures are assumed to
be representative of the machines produced by each manufacturer. There is no infor-
mation readily available indicating the variance associated with each manufacturer's
production models.
Rgure 7 shows the distribution of noise levels as a function of power-to-weight
ratio (in pounds/tip). There appears to be very little correlation. The mean power-to
weight ratio is 12.7 poundsAp. Similar analyses were conducted for maximum ipm,
weight and horsepower, but in all cases, noise levels bear little correlation to these
engine parameters. The average horsepower of all models is 31.3 hp and the average
maximum engine speed is 6350 rpm.
Rgure 8 shows the relation between noise level and retail price. Snowmobile
prices range from about $600 to $1800, but most of them are priced between $800 and
$1400, with a mean retail price of $1146. There is no correlation between snowmobile
price and noise level.
Since there is no obvious relation between snowmobile noise levels and other
engine parameters, it is not reasonable to categorize current models by any of these
quantities. Furthermore, there is no definite separation by utilization for snowmobiles,
as they are used almost exclusively for recreation. Hence, they may not be grouped
by their intended use. Throughout this report, therefore, snowmobiles will be treated
as belonging to one single class.
A typical one-third octave band spectrum of snowmobile noise is shown in Figure 9.
An interesting feature of the frequency dependence of noise is the ability to identify
12
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£•>
84
83
New York State
* 1973^tandard
81
.3
s
*5
78
77
-§>
• Average Level
eo
-a
•5 79
o
I
I
New York State
1976 Standard
I I
75
74
200 300 400 500 600
Engine Displacement, cc
Source: Reference 8.
Figure 5. Noise Levels of 1973 Model Snowmobiles as a Function of
Engine Size (Data Points Represent Measurements Made per
SAE J192 Test Procedure on a Grass Covered Test Site)
(Group 1 - Large Manufacturers)
13
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83
«E 82
Z
CO
TJ
I
s
*0
•O
1 .
New York State
1973 Standard
81
J. 80
a>
i£
S 79
78
77
76
75
•• * Ayera£e_Leye^
New York State
1976 Standard
74
200
1
1
300
400 500
Engine Displacement, cc
600
Source: Reference 8.
700
Rgure 6. Noise Levels of 1973 Model Snowmobiles as a Function of
Engine Size (Data Points Represent Measurements Made per
SAE J192 Test Procedure on a Grass Covered Test Site)
(Group 2 - Smal I Manufacturers)
14
-------
CO
-o
V
0)
o
z
CD
"«
84
83
82
81
80
? 79
78
77
76
75
74
**
•••
••*
Represents Two
Data Points
••••
• •
1
10
Source: Reference 8.
15
20
LBS/HP
25
30
35
40
Figure. 7. Noise Levels of 1973 Model Snowmobiles as a Function of
Power/Weight Ratio (Data Points Represent Measurements Made per
SAE J192 Test Procedure on a Grass Covered Test Site)
15
-------
CN
84
83
eo
-o
81
80
B 79
S 78
"o
•o
J 77
o»
75
74
200
I I I I I
• • • • •
• . •
,1 • I AA •
k • •• • •
•
• • ••
A Represents Two Data Points
• Represents Three Data Points
I
400
600
800 1000 1200
Retail Price, Dollars
1400
1600
1800
Source: Reference 8.
Figure 8. Noise Levels of 1973 Model Snowmobiles as a Function of
Retail Price (Data Points Represent Measurements Made per
SAE J192 Test Procedure on a Grass Covered Test Site)
16
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CM
JE
a.
o
CM
S
CO
TJ
w
J
I
u
o
^
no
100
90
80
70
60
50
40
30
20
10
I T
Air Intake and Muffler
Exhaust Noise
r-Traek Noise
Engine Cooling
Fan Noise
i i i i i i
i i i i i i i i i i l l i I i i i i i
31.5
125
500 2K
Frequency (Hz)
Source: Yamaha International (See Reference 5).
8K
20K
Rgure 9. Typical Snowmobile Noise Spectrum (per SAE J192)
component noise sources. As seen in Figure 9, the peak near 200 Hz may be associated
with intake and exhaust noise; track noise is located in the 500 Hz band and engine
gear noise and cooling fan noise are in the 1000 to 2000 Hz region.
Operator Noise Exposure
Due to their proximity to the engine, snowmobile operators and passengers are
exposed to noise levels that may result in permanent hearing damage. A recent study
found evidence of temporary threshold shift (an indication of permanent hearing damage
risk; noise exposures that produce temporary threshold shift in normal ears may ulti-
mately produce permanent hearing loss under conditions of repeated exposure) in
17
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87 percent of the operators tested after as little as 30 minutes of exposure/ This
indicates that many snowmobile riders are exposed to noise levels that could poten-
tially result in permanent hearing loss over a long period of time. Furthermore,
high noise levels at the operator's position prevent him from hearing warning signals
such as train whistles and therefore present a definite safety hazard.
In spite of the importance of operator noise exposure, little accurate data is
available on actual operator noise levels. A measurement standard is needed that
will provide reliable, accurate measurements. Two methods of measuring operator
exposure have been proposed; one involves the use of a miniature microphone to mon-
itor the noise at the operator's ear and the other measures noise at the operator's
normal ear position without the operator present/ Either of these methods should
result in reliable measurements without the inaccuracies inherent in sound level meter
readings made behind the operator's head.
It would be convenient to be able to relate operator noise exposure to noise
levels recorded at 50 feet as this would allow simple field monitoring of operator
noise levels with a sound level meter. However, each snowmobile has unique noise
radiation characteristics and a simple relation between the two levels has yet to be
established.
The data in Table 2 presents operator noise levels and levels measured at 50 feet
for 12 different 1973 production model snowmobiles. Noise levels at the operator's
ear range from 98 to 114 dBA and noise levels measured at 50 feet range from 78 to
87 dBA. The difference between operator noise level and noise level at 50 feet
ranges from 17 to 32 dB. Obviously, the desired relation between the two levels is
not available, at least for field measurements made in accordance with the SAE J192
Standard Test Procedure.
18
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Table 2
Maximum Noise Levels at Operator's Ear and at 50 Feet
Vehicle
A
B
C
D
E
F
G
H
I
J
K
L
2
Level at Operator's Ear,
dBA
114
98
100
100
114
112
111
109
100
106
108
111
Level at 50 Feet,3
dBA
83
81
78
78
87
80
82
80
80
85
86
85
Difference
dBA
31
17
22
22
27
32
29
29
20
21
22
26
'Source: George Gowing (See Reference 4).
2A-Weighted Noise Level in dB re 20 pN/m2.
3A-Weighted Noise Level in dB re 20 |jN/m2 Measured per SAE J192 Test Procedure.
Noise Sources
Individual sources of noise may be categorized into three general groups: exhaust
noise, engine compartment noise and track noise. This breakdown is shown in Rgure 10
o
for a 1973 Cheetah snowmobile manufactured by Arctic Enterprises although the com-
ponent noise levels are typical of machines made by other manufacturers.
Exhaust Noise
Exhaust noise is generated by combustion air moving out of the engine in pulses
that radiate energy in the 100 to 200 Hz frequency range. For several years, exhaust
19
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Muffler Shell
Noise
78*
Intake
Noise
73
Engine
Noise
78
Fan Noise
81
Other
73*
Unattenuated Engine
Compartment Noise
85
Hood Attenuation
Exhaust
Noise
74
Attenuated
Engine Compartment
Noise
80
Track
Noise
73*
Overall Noise Level
81.5dBA
Source: G. Englert (See Reference 3).
Calculated Values. All values are
A-weighted noise levels, dBA.
Figure 10. Synthesis of Representative Snowmobile Component
Noise Sources into an Overall A-Weighted Noise Level
20
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noise was the dominant noise source in snowmobiles. The noise spectrum of Figure 9 for
a 1971 model shows that along with intake noise, the exhaust is the largest noise con-
tributor. Recent improvement in exhaust mufflers and intake silencers have reduced the
magnitude of this contribution as the data in Figure 10 for a 1973 model indicates.
Engine Noise
Engine compartment noise is composed of mechanical noise radiated from the
engine surfaces, carburetor intake, cooling fan, muffler shell, and miscellaneous
sources. All these sources are lumped together under the cowl or hood making up one
of the three major noise sources.
Engine noise is produced primarily by vibration of engine surfaces as a result of
combustion within the engine. Any parts attached rigidly to the engine also become
radiating surfaces. Intake noise is created by combustion within the engine in the same
manner as exhaust noise. Some of the acoustic energy thus created leaves the engine
through the carburetor air intake. Muffler shell noise is due to vibration of the muffler
shell as the exhaust gas pulses through it. Fan noise (associated with fans required to
provide cooling air) is produced by turbulence created as the fan blades move through
the air and the passage of the cooling air over local obstacles. The other noises created
in the engine compartment are associated with vibrations of surfaces attached directly
and indirectly to the engine.
Track Noise
Track noise is associated with the impact of hard surfaces striking each other.
For example, as the track moves over the bogies, sprocket teeth on the bogies must
alternately engage and disengage with the track, creating impact noise. The clanking
of other metal parts in the suspension system also contributes to track noise.
21
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5. SELECTED NOISE LEVELS
The data on noise levels for currently available snowmobiles — see Figure 4 —
exhibits a great deal of scatter. A rational approach can be made to the discussion
of present and future noise levels by focusing attention on a few representative levels.
It has been decided, in consultation with EPA, that three different noise levels will
be examined based on the information and data supplied by the manufacturers. The
three levels may be summarized as follows:
1. Typical level of currently available, quiet products
2. Level of quietest product in October 1975 that incorporates the most
advanced technology
3. A level somewhere between the first two, if these two are widely divergent,
that can be practically obtained using available technology by October 1975.
The first level is to be that of typical, currently available, quiet snowmobiles.
Currently available products are defined as those that were being sold in April 1973 —
the date that this study was initiated. This would be the 1973 model snowmobile.
Level 'l indicates where the industry stood in terms of noise control technology at the
start of this project.
The value of Level *1 may be determined from an examination of the noise data
for existing snowmobiles shown in Figure 4. The mean level for all 215 models shown
is slightly in excess of 81 dBA. However, if those models exceeding the New York
State requirements of 82 dBA are not counted, the mean level is approximately 80 dBA.
The models exhibiting noise levels less than about 78 dBA represent only about 5 percent
of those for which data is available and hence are not typical. As a result, a typical
quiet snowmobile, as sold in April 1973, exhibits a noise level in the range 78 to 82 dBA,
the mean being approximately 80 dBA. This is Level *1.
The second level will be that of the quietest model snowmobile that is expected to
be available in October 1975, the anticipated effective date for Federal noise regula-
tions and will consist of the 1976 model year for snowmobiles. This assumes one year
22
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for compliance with the regulations. In selecting the quietest 1976 snowmobile, some
judgement must be used in selecting a model that fulfills the operational requirements
of snowmobile users. That is, the machine must be of a popular size, have good per-
formance characteristics and not be overly heavy. Not every quiet snowmobile can
be considered as a candidate. Small, quiet machines that do not have sufficient speed
or power, and large, heavy machines that tend to bog down in loose snow should not be
considered because their performance characteristics have been radically changed, even
though they may be very quiet. One 1974 model snowmobile has been measured and
certified at 76 dBA. This model is a popular size in the range of 400 to 440 cc and
weighs approximately 400 to 450 pounds. The manufacturer of this snowmobile has indi-
cated that he anticipates a level of 74 dBA from this snowmobile for the 1976 model
year (those made in 1975).
Other manufacturers have indicated reasonable progress in noise control and it
is likely that the 1976 model year will see many snowmobiles with noise levels as low
as 74 dBA. There is no indication from any of the manufacturers that levels lower than
this can be obtained. It seems quite reasonable then, that Level *2 should be 74 dBA.
The third level selected is to be between the first two if these are widely sep-
arated. Such a condition would indicate creative application of technology known
only to some manufacturers. Since not all manufacturers could comply with a regulation
set at Level ^2, Level ^3 is proposed as an intermediate level.
Clearly, not all snowmobile manufacturers will be able to comply with a 74 dBA
noise level by 1976 even though several will be able to do so. A value for Level *3
chosen somewhere between 74 dBA and 80 dBA would insure a greater degree of com-
pliance among manufacturers. The International Snowmobile Industry Association (ISIA)
has proposed 78 dBA for the 1976 model year. This organization includes in its member-
ship 18 major snowmobile manufacturers accounting for approximately 90 percent of all
snowmobifes manufactured. It is the opinion of Wyle Research, based on information
supplied by manufacturers and our own engineering experience in noise control, that a
23
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reasonable level for the 1976 model year would be 76 dBA. Without relying on new
technology, manufacturing firms representing approximately 60 percent of the market
should have the capability of complying with a 76 dBA level for 1976. All three levels
that have been discussed are summarized below in Table 3.
Table 3
Selected Noise Levels for Potential Noise Regulation of Snowmobiles
Level
1
2
3
Interpretation
Currently Available Snowmobile Levels
Quietest Snowmobile October 1975
Practically Attainable Level by
October 1975
Value "
80 dBA
74 dBA
76 dBA
24
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6. NOISE REDUCTION TECHNIQUES AND COSTS
In Chapter 5, three selected noise levels were developed for snowmobiles. This
chapter will discuss existing technology for reducing noise from individual snowmobile
noise sources. The cost of applying this technology to achieve the three selected noise
levels will then be presented.
The terms of this study emphasize cost to the manufacturer as an important con-
sideration. The data collection effort was structured to be consistent with this require-
ment — requesting data for a variety of noise abatement measures from the manufacturer.
In some instances, manufacturers furnished the information requested; in others, however,
they supplied a variety of direct and indirect cost elements which they expect to incur.
In all cases, manufacturers supplied cost data for noise reduction to discrete levels, in
particular, 78 dBA, 76 dBA, 75 dBA and 73 dBA, since these four levels have been
attained or have been proposed by various regulating agencies as reasonable levels for
snowmobile noise emission.
Three observations are appropriate for the proper interpretation of the data pre-
sented. The first problem requiring explicit exposition is the relationship between direct
expenditures incurred by manufacturer in noise abatement endeavors and the accounting
practices associated with these expenditures. The recording and burdening of direct
cost varies among suppliers according to their cost accounting systems and cannot be
specified in a general sense. Furthermore, in cases where tooling and design expend-
itures are involved, the specific unit cost will depend on the expected production runs
for the model under consideration, a variable which might change considerably over
time.
For these reasons, a definitive, defensible overall relationship between "cost to
manufacturer "and "cost to the consumer" is difficult to establish. However, in certain
instances where only consumer costs were provided, such a relationship must be assumed.
Although manufacturing overhead, general and administrative expenses, distributor and
retailer markups customarily increase consumer prices many times the direct cost of
25
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production, the competitive characteristics of the snowmobile industry limit somewhat
the total increase in cost to the consumer. Manufacturers who submitted both manu-
facturers and consumers cost information showed a difference between the two costs
ranging from a factor of 2 to a factor of 3. Therefore, when only consumer costs were
available, the manufacturing costs were assumed to be smaller by a factor of 2.5.
The second observation is the obvious limitation of some of the data provided by
manufacturers. Snowmobile manufacturing firms display a wide range of organiza-
tions. At one end of the spectrum are firms with large engineering departments staffed
with noise specialists capable of using sophisticated equipment for making noise measure-
ments, as well as evaluating the effectiveness of new noise reduction techniques. The
other end of the spectrum is populated with small firms who cannot afford to allocate
funds for engineers trained in noise control and special noise measuring equipment.
Obviously, with such differing capabilities in noise control, the data supplied by the
manufacturers varied from empirical results to well-substantiated engineering projections
to mere conjecture. Accordingly, an attempt was made to separate all data into two
groups; those based on good engineering practice and those based on conjecture.
All noise levels in this report are assumed to be median levels for each produc-
tion run. That is, there is a normal spread in the levels produced by all the machines
in each model line. Due to a lack of data, the magnitude of this spread is not accurately
known, but it seems reasonable to assume it is about 4 dB wide and centered about the
median. Thus for all models (at least 90 percent) to be below a particular level, the
design goal will have to be depressed by 2 dB.
All estimated costs contained in this report correspond to this median level. Any
depression of the noise level goal will, of course, be reflected in proportionally higher
costs.
All estimated costs also assume adequate development time as discussed under a
separate heading.
26
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Noise Reduction from Subsources
There are two basic approaches to any noise reduction problem; one is to control
noise at its source by appropriate engineering methods, the other is to prevent trans-
mission of noise, once it is created, by interruption of the transmission path with barriers
or enclosures. Some noise sources are more amenable to the first technique, some to the
second, and some to a combination of the two.
The following discussion is not intended to be a definitive engineering guide to
snowmobile noise control, but is merely a summary of some of the available techniques
and methods that may find practical application in snowmobile noise reduction. It is
important to realize that reduction of overall noise levels will be accomplished only
when all contributing noise sources are treated. For example, the 1973 model snow-
mobile outlined in Figure 10 was fitted with a new stock muffler system designed for
production. The new muffler reduced exhaust noise from 74 to 68 dBA, but the measured
overall noise level was reduced only 0.5 dB from 81.5 to 81 dBA. This is due to the
manner in which acoustic energy from multiple sources combines.
Engine Compartment Noise
Engine compartment noise includes all the noise sources under the hood producing
levels in the order of 85 dBA. The hood provides an approximate attenuation of only
5 dB due to poor sealing and the presence of large cooling air louvers. A well designed
hood should be capable of attenuating the interior noise by 10 dB. This source of noise
may be reduced by applying both general methods of noise reduction; the sources in the
compartment may be quieted and the attenuation of the hood may be improved.
The major difficulty in improving hood attenuation is the requirement for cooling
air which is essential for safe operation. The need for adequate engine cooling is a legit-
imate design constraint. Fan-cooled engines allow for more complete hood enclosures than
do forced air engines (used for high speed machines and racers) which do not use a fan at
all. It seems unlikely that the present concept of a Free Air Snowmobile is compatible
with noise emission below 80 dBA. Fan-cooled engines are more amenable to noise control
than are free air engines, since the engine compartment hood may be more fully enclosed.
27
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A third type of engine which is water cooled has better possibilities still, even though it
requires a cooling fan since the engine compartment may be fully enclosed. It has been
estimated by some manufacturers that the cost to change from an air-cooled to a liquid-
cooled engine would be in the range of $30.
If an air-cooled engine is retained, a cost of approximately $7 per machine would
be incurred to improve the hood sealing and secure open-cell polyurethane foam absorp-
tion material to the interior. In addition, air cooling louvers can be of a minimum size
that will provide sufficient air flow for cooling. Judicious placement of the louvers so
that noise radiating from them is directed downward as much as possible will help reduce
operator exposure levels as well as exposure levels for distant observers. It may prove
to be practical to utilize acoustical louvers that are acoustically absorptive on the interior
side so as to allow free air passage in one direction while blocking noise propagating in
the other. Such louvers are now in common use for noise reduction in mechanical equip-
ment, but should be considered advanced technology for snowmobiles.
Within the engine compartment several noise sources can be quieted; including
the engine, the cooling fan, the muffler shell, and the carburetor intake. The engine
can be mounted on vibration control mounts of a proper size corresponding to the weight
and vibration frequency of the engine. In a recent study of quiet snowmobiles, some
success in reducing induced vibration was achieved by coating the engine compartment
| r\
floor and frame members with automotive cork-filled undercoat material.
The cooling fan can be chosen for quiet operation. Fan noise technology is well
advanced and manufacturers can make use of this technology described in the noise con-
trol literature. The quietest fan for any application is the one that operates near peak
efficiency and cooling fans should be selected with this in mind. The cooling air can
be ducted in and out with absorptively lined ducts to decrease radiated noise. Again,
technology for quiet air flow ducting is established and well documented in the
literature.
Muffler shell noise presents some unique problems. Some manufacturers have
reduced this noise by wrapping the muffler with an absorptive material (such as
28
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fiberglass) covered with sheet metal, but others claim that using space for a large muf-
fler would lead to overheating in the engine compartment. Still others have placed a
wrapped muffler outside the engine compartment, but there are those who maintain
that an external muffler will melt snow and the resulting water will refreeze on other
parts of the snowmobile. A valid suggestion made by an independent research group
is to use a flexible exhaust pipe or flexible connections to isolate the muffler from
the rest of the engine compartment. This will reduce noise to a certain degree by
reducing the vibration of other components.
Carburetor intake noise has been quieted to some extent in the last few years by
addition of intake silencers. Intake noise is less important now than other engine
compartment sources. The technology for improving the efficiency of intake silencers
is available and the cost to install an improved silencer necessary to reduce intake
noise would range from $4 to $8.
Exhaust Noise
Exhaust systems are currently available which utilize an expansion chamber
incorporated in a tuned system. This configuration helps to scavenge spent gases from
the engine and so is more efficient than a conventional muffler (or no muffler) both
for noise suppression and power output. Exhaust noise is no longer a major contributor
to overall noise due to the widespread use of tuned exhaust systems. Exhaust noise
levels on the order of 68 dBA are feasible and an estimated manufacturers cost for the
addition of a system to achieve such a level is approximately $13.
Track and Suspension Noise
Noise produced by the track and suspension system can only be reduced through
design since baffling techniques are not practical. Track and suspension noise is cur-
rently on the order of 73 dBA, although some manufacturers have reduced track noise
below this level. A widely held belief is that track noise is the "noise floor" for
snowmobiles and is not amenable to treatment. There seems to be some contention as
29
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to just- where this floor is, however. One manufacturer performed tow-by tests without
the engine running and reported passby levels of 74 dBA in grass and 63 dBA is snow.
Another manufacturer engaged a private engineering firm to study the basic sources of
snowmobile noise. Their tests indicated that track noise was on the order of 62 dBA
in grass. Still another manufacturer has indicated that it should be feasible to reduce
track and suspension noise to a level necessary to meet an overall noise level of 73 dBA.
An estimated cost for this engineering work is approximately $6 per machine.
Operator Noise Exposure
It should be noted that working on the problem of reducing operator noise expo-
sure will benefit efforts to reduce noise levels measured at 50 feet. The converse is
not always true, however, since by changing the vehicle's noise directivity pattern,
levels measured at 50 feet may be reduced without reducing levels at the operator's
ear position. An example of this would be installation of noise baffles causing the
sound to be directed to the front and to the rear of the snowmobile. Levels measured
in accordance with the SAE J192 standard may then be reduced without a corresponding
reduction in the noise levels at the operator's position.
The benefits of reducing operator noise exposure are substantial and since reduc-
tions in levels at 50 feet accompany reductions in levels at the operator's position, it
would seem that industry's efforts should be aimed at reducing operator noise level.
However, as discussed in the section on Operator Noise Exposure, techniques for
measuring noise at the operator's position are not well defined. So until standard
measurement procedures are developed, noise control efforts will have to be directed
towards reducing noise levels at 50 feet.
30
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Achievement of the Selected Noise Levels Through Application of Noise Reduction
Techniques
The previous discussion of techniques to reduce noise emitted from various sources
has focused on reducing mechanical, intake, exhaust and track noise. The noise control
cost information developed for these subsources can now be combined to determine the
total costs of noise reduction to the three selected noise levels developed in Chapter 5.
Table 4 shows the estimated manufacturing cost increases along with the required
modifications to reduce overall noise to each of the three levels. The data shown are
estimates made by Wyle Research, based on data supplied by some of the manufacturers
in Group 1 (Large Manufacturers). The manufacturers who supplied component cost data
represent about 34 percent of the snowmobile market. This 34 percent of the market may
be considered as representative of the industry as a whole since the total machine costs
in Table 4 compare very well with total machine costs presented in Figures 11 and 12
and Table 5 which are based on information supplied by manufacturers representing
70 percent of the snowmobile market.
All manufacturing costs in Table 4 are given for each noise control component or
required work necessary to reduce noise to the level shown. For Levels ^2 and ^3, two
alternatives are considered — retainment of air-cooled engines or changeover to liquid-
cooled engines. The liquid-cooled engine is not considered to be an economically
valid alternative for reduction to Level *1 —80 dBA. Rotary engines were not considered
as viable alternatives to reciprocating-piston engines due mainly to a lack of data.
Although some manufacturers have indicated that rotary engines are quieter than recip-
rocating piston engines, there has been no demonstration that they possess appreciable
advantage over reciprocating-piston engines for noise control purposes.
Many manufacturers supplied data in the form of total cost per machine. This
data is presented in Figures 11 and 12 for Groups 1 and 2 respectively. All costs are
given for reduction of noise with a baseline reference of 82 dBA. There is a great
deal of variation in the estimated costs anticipated by various manufacturers and the
spread in the estimates for each noise level tends to increase as the level gets pro-
gressively lower.
31
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CO
Table 4
Estimated Per-Machine Manufacturing Cost Increases for Noise Reduction in Snowmobiles
Component
Engine
Compartment
Exhaust
Track and
Suspension
Selected
Noise Level
N. Engine
N. Alternate
RequireaN.
Worker \v
Component N^
Engine
Modifications
Intake Silencer
Acoustic
Treatment of
Console and
Hood
Air Ducts and
Baffles
Improved
Muffler
Isolation
of Axles
Track Redesign
TOTAL COST
#1
80dBA
Air Cooled
$6
$4
$ 7
N.R.
$5
N.R.
N.R.
$22
#2
74dBA
Air Cooled
$55
$ 8
$4
$4
$13
$ 4
$2
$90
Liquid Cooled
$32
$ 8
$4
N.R.
$13
$4
$ 2
$63
' #3
76dBA
Air Cooled
$20
$ 8
$4
$4
$13
N.R.
N.R.
$49
Liquid Cooled
$32
$ 8
$4
N.R.
$13
N.R.
N.R.
$57
The costs presented are estimates to reduce the noise from a model line to an average value as indicated. Data is
based on information from manufacturers representing 34 percent of the snowmobile market. All component cost data
shown in Table 4 was supplied by firms in Group 1 (Large Manufacturers).
-------
300
250
o
Q
c200
o
o
D
150
o
-------
300
e
_c
•- 200
0
o
o
u
100
O
£
a
o
50
10
Manufacturer's
Conjecture
Estimates
Based on
Engineering
Data
82 80 78 76 74 72
A-Weighted Noise Level - dB re 20pN/m2
Figure 12. Estimated Manufacturing Costs for Snowmobile Noise Reduction as a
Function of Level Obtained (Costs are Based on Noise Reductions
from 82 dBA) (Group 2 — Small Manufacturers)
-------
It is interesting that one manufacturer did, in fact, save money in the process of
quieting his snowmobile. These data points represent actual costs incurred. It should
be noted that this is a manufacturing cost saving only in the context of a noise reduc-
tion from 82 dBA to 78 dBA. After spending $26 per unit to reduce noise from 86 dBA
to 82 dBA, a change in the design of the intake silencer-system resulted in lower cost
and a quieter machine. It is not expected that other manufacturers would be capable
of similar cost savings, but this isolated case does indicate that making a snowmobile
quieter is not always associated with a manufacturing cost penalty.
A summary of the costs involved to reduce noise to the three levels discussed in
Chapter 5 is shown in Table 5. These costs were determined by calculating the aver-
age value of the shaded portion of the graphs in Rgures 11 and 12 at each of the three
levels of interest. The costs in Table 4 are direct manufacturing costs in dollars.
The data shown in Table 5 are, in the opinion of Wyle Research, accurate
estimates of costs that would be incurred to reduce noise to the indicated levels. The
$180 cost for reduction to 74 dBA may be high, but is probably a direct reflection of
the approach to noise reduction being used by the smaller firms in Group 2.
Basic engineering and design changes are likely to be favored as a noise control
approach by the larger firms in Group 1. These changes are initially expensive for
the first few stages of reduction, but get progressively less expensive at the more
advanced stages. The technique of absorbing or shielding noise, once it is created,
is probably the only approach a smaller firm can adopt because of its limited resources.
This technique is initially inexpensive for small stages of reduction, but as the target
noise level gets lower, this 'band-aid" approach becomes very expensive. Hence,
as seen in Table 5, Group 2 manufacturers incur a lower cost for reduction to Level "1 -
80 dBA than do Group 1 manufacturers. For a reduction to Level *3 - 76dBA, both
groups would incur about the same cost whereas for a reduction to Level *2 — 74 dBA,
it would be much more costly for the Group 2 manufacturers than for the Group 1
manufacturers. The costs given in Table 5 for Group 1 compare favorably with the
35
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Table 5
Summary of Estimated Noise Reduction Costs for Snowmobiles1
Level
1
2
3
Noise Level Goal
80dBA
74dBA
76dBA
Group 1
$22 ( 2%f
$86 ( 8*)
$52 ( 5%)
Group 2
$ 9 ( H)
$180 (16 $
$ 45 ( 4%)
Based on information supplied by manufacturers representing 70 percent of the
snowmobile market. Costs are estimates to reduce noise from a model line to
an average value as indicated.
2Numbers in parentheses are percentage increases based on an average retail
price of $1146.
3The $180 cost anticipated for Group 2 for reduction to 74 dBA is based on
data from one manufacturer. It was considered to be a guess as opposed to
an estimate based on engineering data.
component cost totals given in Table 4 and they are more representative of the industry
as they were compiled from information supplied by manufacturers representing 70 per-
cent of the snowmobile industry.
Weight Increases Due to Noise Reduction
Weight increases are very important to snowmobile manufacturers because of
snow flotation problems discussed in Chapter 4. Overly heavy machines may bog down
in loose snow and hence present a hazard where snow conditions change from hard-
packed snow to loose powder. Most popular sized snowmobiles weigh between 300 and
450 pounds with an average weight of 398 pounds.
Added weight due to noise reduction is first evident in the form of added silenc-
ing equipment such as mufflers and intake silencers. Additional silencing may require
heavier engine compartment panels and heavier engine mounting frames.
36
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Weight increases attributable to noise reduction are shown in Figures 13 and 14
for all manufacturers in Groups 1 and 2. Again, there is a wide spread in the data
at each noise level and the spread tends to increase as the level decreases.
In general/ each decrease to a level below 82 dBA is accompanied by an increase
in weight. There was one response, however, that indicated a noise reduction with
no weight penalty. A weight increase was encountered to reduce noise from 86 dBA
to 82 dBA, but for the reduction from 82 dBA to 76 dBA, no extra equipment was added.
Table 6 indicates the median level of weight increases as a direct result of noise
reduction techniques. The data taken as median values from the graphs in Figure 13
and 14 is given in added pounds and in percent increases in weight based on an
average snowmobile weight of 398 pounds.
-8
D
0
a
I
73
12
66
60
54
48
42
36
30
24
18
12
6
82 80 78 76 74
A-Weighted Noise Level - dB re 20 M N/m2
Figure 13. Estimated Snowmobile Weight Increase Due to
Noise Reduction Equipment (Data Based on
Noise Reduction from 82 dBA)
(Group 1 - Large Manufacturers)
37
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1
I
1
o
c
o>
1
72
tt
60
54
48
42
36
30
24
18
12
6
82 80 78 76 74
A-W«ighted Noise Level - dB re 20 [a N/m?
Rgure 14. Estimated Snowmobile Weight Increase Due to
Noise Reduction Equipment (Data Based on
Noise Reduction from 82 dBA)
(Group 2 - Small Manufacturers)
Table 6
Estimated Snowmobile Weight Increase Due to Noise Reduction1
Level
1
2
3
Noise Level Goal
80 dBA
74 dBA
76 dBA
Group 1
12 ( 3$2
52 (13$
30 ( 8%)
Group 2
15 (44)
61 (15$
48 (12$
Based on information supplied by manufacturers representing 70 percent of the
snowmobile market.
2
Numbers in parentheses are percentage increases based on an average weight
of 398 pounds.
38
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Lead Time Requirements
One of the major difficulties in a product noise reduction program is lead time —
the time required for engineering, testing and tooling. During the data gathering phase
of this study, manufacturers were asked to comment on their lead time requirements.
Most manufacturers indicated the necessity of having sufficient lead time and several
firms supplied lead time schedules. The schedules submitted varied widely due to dif-
ferent levels of effort that individual firms thought were necessary for noise reduction
modifications. Manufacturers who anticipated major engineering and design changes
indicated long lead time requirements and those who did not anticipate major changes
indicated shorter requirements. The typical lead time schedule discussed below is, in
the opinion of Wyle Research, adequate for noise reduction efforts to reach a goal of
76 dBA (Level *3 as discussed in Chapter 5). Of course, if lower noise levels are
required, the necessary lead time will increase appropriately. The schedule is based
on information supplied by snowmobile manufacturers representing approximately 43
percent of the snowmobile industry.
Sales for the 1976 model year snowmobile will begin in June of 1975 for most
firms. The machines will be produced throughout most of 1975 with an average produc-
tion start date of March 1975. The average time period required for tooling and testing
is 9 months so engineering efforts will be frozen in June 1974. Any engineering work
required for noise reduction will have to be accomplished before this date. However,
as seen in Table 4, major engineering changes will not be required for a reduction to
76 dBA. But, if manufacturers are required to reduce noise levels below 76 dBA, major
engineering work will be required and the needed development time will exceed the
time available in this schedule.
It was estimated in Chapter 5 that manufacturing firms representing approximately
60 percent of the snowmobile market have the capability of complying with a 76 dBA
level within the estimated lead time schedule. If the effective date for regulation of
snowmobile noise is extended from October 1975 to October 1976, then the percentage
of manufacturers who will be able to comply will increase. It is estimated that at least
80 percent and perhaps as much as 90 percent of the market will be able to comply
with a 76 dBA level with one extra year for development.
39
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7. RECOMMENDATIONS FOR FURTHER WORK
As a result* of this study, it was determined that further research is needed in the
following areas:
• The SAE J192 test procedure needs to be reviewed for applicability as a
regulatory tool. The SAE Subcommittee for Motorized Snowvehicles is
presently working on new revisions. One major question that needs to be
settled is the test surface to be used. One test surface must be found that
gives accurate, repeatable results and is available to all manufacturers for
a sufficient number of testing days.
• A study is needed to determine if any correlation can be established between
operator noise levels and levels at 50 feet. If no correlation exists, then con-
sideration should be given to a procedure for accurately determining noise
levels at the operator's position. Regulations to maintain operator noise
exposure within acceptable limits should then be considered.
• Research on typical use cycles of snowmobiles is needed to develop a data
bank that accurately reflects the typical noise exposure of snowmobile
operators.
• Research on the variance in noise levels for snowmobiles in each model line
is required to determine the actual distribution of noise levels. Such infor-
mation would be helpful in determining the anticipated compliance with
noise level regulations.
40
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REFERENCES
1. Hare, C.T. and Springer, K.J., "Exhaust Emissions from Uncontrolled Vehicles
and Related Equipment Using Internal Combustion Engines, " Southwest Research
Institute, September 1973.
2. Wimer, S., Editor, Invitation to Snowmobiling Magazine, private communication
to the authors.
3. Engler, G., Arctic Enterprises Inc., private communication to the authors.
4. Gowing, G., "Bombardier's Position on Snowmobile Noise Level Suppression,"
July 12, 1973.
5. Yamaha International Corporation, Buena Park, California, Technical Data on
Snowmobile Noise.
6. Lamont, J., Polaris and Rose, J., Massey-Ferguson, Inc., private communication
to the authors.
7. Chaney, R.B., Me Gain, S.C., University of Montana, Missoula and R. Harrison
Forest Service Equipment Development Center, San Dimas, California, "Relation
of Noise Measurements to Temporary Threshold Shift in Snowmobile Users. "
8. New York State Parks and Recreation, Snowmobile certification data.
9. Harrison, R., Equipment Development Center, U.S. Forest Service, San Dimas,
California, private communication to the authors.
10. Memorandum from Dr. Ben Sharp, Wyle Research, to Mr. Hugh Kaufman, U.S.
Environmental Protection Agency, July 19, 1973.
11. Private communication to the authors.
12. Cowl Industries Limited, "A Study of the Feasibility of Reducing Snowmobile
Noise, " Information Canada, Ottawa, 1973.
13. National Research Council of Canada, Division of Physics, APS-488, "Snow-
mobile Noise —Its Sources, Hazards and Control, " Ottawa, 1970.
41
-------
APPENDIX A
Snowmobi le Manufacturers Contacted for This Study
Alouette
Featherweight Corporation
Montreal 364 Quebec, Canada
Alsport, Inc.
84 Whittlesey Avenue
Norwalk, Ohio 44857
Arctic Enterprises, Inc.
Box 635
Thief River Falls, Minnesota 56701
Auto Ski, Inc.
P.O. Box 97
Levis, Quebec,
Autotechnic Inc. - Ski-Zoom
2300 LeMire Blvd - Drummondville
P.Q., Canada
Boa-Ski., Inc.
P.O. Box 460
La Guadeloupe
Frontenac County, P.Q., Canada
Bombardier Ltd. (Ski-Doo/Moto-Ski)
Val court
P.Q., Canada
Brutanza Engineering
P.O. Box 158
Brooten, Minnesota 56316
Chaparral Industries
Denver,, Colorado 80216
Coleman Skiroule
Route 13
Wickham, Quebec, Canada
Columbia Div. of MTD Products Inc.
5389 West 130th Street
Cleveland, Ohio 44111
John Deere & Co.
John Deere Horicon Works
Horicon, Wisconsin
Fun Seasons, Inc.
1200 Riverwood Drive
Bumsville, Minnesota 55337
Gilson Snowmobiles
Road America Grounds
Elkhart Lake, Wisconsin
Griswold Swinger
1212 Chestnut Avenue
St. Paul, Minnesota 55403
Harley-Davidson Motor Co., Inc.
3700 West Juneau Avenue
Milwaukee, Wisconsin
Herter's Inc.
Plant 1
New Rich I and, Minnesota 56072
Jac-Trac Inc.
Route 2
Marshfield, Wisconsin 54449
Lori Engineering Corporation
Old Turnpike Road
Southington, Connecticut 06489
Massey-Ferguson, Inc. (Ski-Whiz)
1901 Bell Avenue
Des Moines, Iowa 50315
A-l
-------
Melvin Manufacturing Company
Dryden, Maine 04225
Mercury Marine
Fond Du Lac, Wisconsin
Moto-Kometik, Inc.
P.O. Box 490
St.Jean Port-Joli, Quebec, Canada
Northway Snowmobile Ltd.
100 Hymus Blvd.
Point Claire, Quebec, Canada
OEM Ltd.
584 Clinton Avenue
Sudbury, Ontario
Canada
Ontario Drive and Gear, Ltd.
P.O. Box 280, Bleams Road
New Hamburg, Ontario, Canada
Outboard Marine Corporation
4143 North 27th Street
Milwaukee, Wisconsin 53216
Polaris
Roseau, Minnesota
Leisure Vehicles, Inc. (Raider)
2766 Elliott
Troy, Michigan 48084
Raybon Manufacturing Company, Inc.
25 George Street
Wallingford, Connecticut 06492
Roll-O-Flex
Regina, Saskatchewan, Canada
Rupp Industries, Inc.
1776 Airport Road
Mansfield, Ohio 44903
Scorpion
Crosby, Minnesota 5644
Sno-Jet, Inc.
P.O. Box 246 - Ouellet Blvd.
Thetford Mines
P.Q., Canada
Speedway, Inc.
160 E. Longview
Mansfield, Ohio 44905
U.S. Sports
Riverside Airport
Marcy, New York
U.S. Suzuki
Santa Fe Springs, California 90670
Yamaha International Corporation
6600 Orangethorpe Avenue
Buena Park, California 90620
A-2
-------
APPENDIX B
Design Features, Retail Costs and Measured Noise Levels for
1973 Snowmobile Models1
Manufacturer
Alouette
A 1 sport
Arctic
Model
Mini -Brute
Sno Duster
Escort I
Escort II
Venture 440
Eliminator 295
Eliminator 340
Eliminator 440
Sno Brute 340
Sno Brute 440
MTS-30
TS-50
TS-100
TS-100L
TS-125
TS-125L
TS-150
TS-290
STS-290
STS-340
Lynx 292
El Tigre 250
El Tigre 340
El Tigre 400
El Tigre 440
Puma 440
Cheetah 340
Cheetah 400
Cheetah 440
Panther 295
Panther 340
Panther 400
Panther 440
Engine Size
209 cc
295 cc
292 cc
291 cc
436 cc
291 cc
338 cc
435 cc
338 cc
436 cc
165 cc ,
200 cc
200 cc
200 cc
246 cc
246 cc
230 cc
290 cc
290 cc
340 cc
292 cc
245 cc
339 cc
398 cc
436 cc
436 cc
339 cc
398 cc
436 cc
294 cc
339 cc
398 cc
436 cc
HP
5
20
22
22
30
24
28
35
28
40
3
5
5
5
7
7
14
21
21
26
19
N/A
37
43
47.5
N/A
31
N/A
37
19
31
N/A
37
Maximum
RPM
3600
6500
6500
8000
6500
8000
8000
8000
8000
8000
3600
3600
3600
3600
3600
3600
5900
6500
6500
6500
6000
7500
7500
7500
7500
6500
6500
6500
6500
6500
6500
6500
6500
Weight
115
337
340
340
410
363
363
368
377
390
125
145
155
155
160
160
240
255
260
260
N/A
365
365
365
370
365
375
375
375
385
385
385
385
Retail
Price
399
699
849
949
1295
1049
1149
1249
1279
1379
299
445
495
535
549
589
679
745
825
805
795
1275
1350
1425
1495
1250
1185
1295
1375
1325
1250
1350
1425
Noise2
Level, dBA
N/A
82
82
82
83
82
83
83
83
83
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
83.7
83.8
N/A
81.7
82
81.7
N/A
80
80.5
81
78.7
79.0
81.5
80.5
B-T
-------
Manufacturer
Auto Ski
Autotechnic
Brutanza
Chaparral
Coleman
Skirouie
Model
Midget 225
Midget 290 SGL
Midget 290 TWN
Bonanza 290
Bonanza 340
Bonanza 440
Spitfire 290
Spitfire 340
Spitfire 440
Spitfire SS 440
Mach 340
Mach 440
Mach 650
Rebel 280
Rebel 290
Rebel 290e
Comet 293
Comet 340
Comet 440
Comet 441
G.T. 440c
LC44
LC29
Firebird 250
Rrebird 295
Firebird 340
Firebird 400
Rrebird 440
Thunderbird 340
Thunderbird 440
SSin 340
SSIII 400
SSIH 440
RT300
RT300E
RT300T
RT340
Engine Size
225 cc
293 cc
290 cc
290 cc
338 cc
436 cc
290 cc
338 cc
431 cc
436 cc
338 cc
431 cc
647 cc
280 cc
290 cc
290e cc
293 cc
340 cc
440 cc
441 cc
440 cc
439 cc
294 cc
242 cc
292 cc
338 cc
394 cc
432 cc
338 cc
432 cc
338 cc
394 cc
432 cc
293 cc
293 cc
291 cc
338 cc
HP
15
20
22
N/A
28
35
N/A
N/A
N/A
36
55
70
110
16
19.5
19.5
24
28
35
38
40
50
30
22
26
31
36
39
31
39
35
42
46
19.5
19.5
24
28
Maximum
RPM
5500
5500
6500
N/A
7200
6500
N/A
N/A
N/A
6500
9500
9500
9500
5500
5500
5500
7200
7200
7000
7000
7000
6500
6000
7500
7500
7500
7500
7500
7500
7500
7500
5500
5500
7000
6000
Weight
325
350
350
350
355
355
355
365
365
375
N/A
N/A
N/A
270
275
300
275
280
285
285
340
395
355
310
320
330
335
340
340
360
320
330
335
354
382
360
360
Retail
Price
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
665
775
895
995
1095
1195
1225
N/A
1745
1495
895
995
1099
1195
1375
1245
1399
1245
1345
1425
799
899
999
1099
Noise2
Level, dBA
N/A
75.6
75.6
N/A
80
79.5
N/A
N/A
79.5
79.5
80
N/A
N/A
84
82
82
82
83
N/A
N/A
N/A
82
82
81.1
'80.9
80.6
81.7
81.5
81.9
82
82
82
81.9
83.2
83.2
80.6
77.9
B-2
-------
Manufacturer
Coleman
Skiroule
(continued)
Columbia/
MTD
John Deere
Evinrude
Feldman Eng.
Fun Seasons
Harley-
Davidson
JAC-TRAC
Model
RT440
RT440E
RTX 300
RTX340
RTX 440
RTX 447
RTW300
340
400
440
400
500
600
JDX4
JDX8
Bobcat SS 30
Bobcat SS 32
Norseman 21
Norseman 27
Norseman 30
TrailblazerSOE
TW30Q
RC-35Q
Snow Flake 400
Sno-Blazer
Y398
Y440
290
399
440
LTD 399
LTD 440
Engine Size
437 cc
437 cc
293 cc
338 cc
437 cc
437 cc
294 cc
339 cc
398 cc
428 cc
339 cc
436 cc
436 cc ,
292 cc
438 cc
399 cc
437 cc
399 cc
437 cc
437 cc
437 cc
437 cc
528 Rotary
340 cc
292 cc
398 cc
433 cc
290 cc
399 cc
440 cc
399 cc
440 cc
HP
35
35
24
34
40
40
23
30
34
38
28
36
36
25
40
30
32
21
27
30
30
30
35
22.5
20
30
35
24
33
38
33
38
Maximum
RPM
6000
6000
6000
6500
6500
6500
6000
7000
7000
7000
6750
6750
6750
6750
6750
6000
6000
6000
5800
6000
5800
5800
5500
N/A
6000
6000
6000
6500
6500
6500
6500
6500
Weight
402
430
356
362
374
404
356
356
358
358
382
386
410
396
386
N/A
N/A
N/A
N/A
N/A
N/A
N/A
520
297
225
400
400
340
340
340
350
400
Retail
Price
1249
1349
1049
1199
1299
1399
1299
1095
1175
1245
1235
1335
1435
995
1435
1075
1145
855
995
1275
1525
1695
1700
695
895
N/A
N/A
795
995
1095
1195
1300
Noise2
Level, dBA
82.1
82.1
83
82.7
80.6
80.6
77.4
N/A
N/A
N/A
81.9
81.7
81.9
81.7
81.7
83.7
82.8
82.9
82.4
83.7
83.1
74.8
77.4
N/A
82.4
81.7
81.6
81.2
81.7
82
81.7
82
B-3
-------
Manufacturer
Johnson
Motors
Kometik
Massey-
Ferguson
Mercury
Marine
Moto-Ski
Northway
Snowmobile
Model
Golden Ghost 30
Phantom 35R
Rampage 30
Rampage 32
Reveler 21
Reveler 27
Reveler 30E
Skee Horse 30
MK-II-225
MK-III-295
MK-III-340
MK-III-340
MK-III-440
340T
400T
440T
400 WT
440 WT
Hurricane-Mark II
Hurricane-Mark I
440 Max-Electric
440 Max-Manual
Cadet 250
Capri 295
Capri 340
Capri 440
Zephyr 340
Zephyr 440
up H 295
"F" 340
"F"440
"S"400
•5-440
Explorer 15-340
Explorer 15-400
Explorer 15-440
Engine Si^e
437 cc
528 Rotary
399 cc
437 cc
399 cc
437 cc
437 cc
437 cc
225 cc
295 cc
340 cc
340 cc
440 cc
339 cc
398 cc
428 cc
398 cc
428 cc
644 cc
644 cc
440 cc
440 cc
247 cc
293 cc
336 cc
435 cc
336 cc
435 cc
293 cc
336 cc
437 cc
399 cc
437 cc
339 cc
398 cc
436 cc
HP
30
35
30
32
21
27
30
30
12.5
20
25
28
37
32
36
40
36
40
50
40
40
40
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
32
N/A
32
25
30
36
Maximum
RPM
5800
5500
6000
6000
6000
5800
6000
5800
5500
5500
6500
6500
6500
6500
6500
6500
6500
6500
6000
6000
6500
6500
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
6000
N/A
6000
N/A
N/A
N/A
Weight
N/A
N/A
N/A
395
N/A
N/A
N/A
N/A
360
310
340
340
340
355
360
365
385
390
490
584
425
395
295
375
390
390
420
420
380
395
395
400
400
360
360
360
Retai 1
Price
1695
1850
1075
1145
855
995
1275
1525
575
785
965
1045
1150
N/A
N/A
N/A
N/A
N/A
1610
1495
1245
1165
595
745
995
1095
1045
1145
1095
1145
1245
1395
1495
N/A
N/A
N/A
Noise2
Level, dBA
73.8
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
81.1
77.5
78.7
79.1
80.7
81.9
82
81.9
82
83.6
83.6
79.7
79.7
79
80.5
81.5
81.5
81.5
81.5
N/A
N/A
82
82
82
80.4
N/A
83
B-4
-------
Manufacturer
Norfhway
Snowmobile
(continued)
Polaris
Raider
Roll-O-Flex
Rupp
Model
Explorer 18-340
Explorer 18-400
Explorer 18-440
Interceptor 15-340
Interceptor 15-440
Interceptor 18-340
Interceptor 18-440
Interceptor 18-650
Colt 175
Colt 250
Colt 295
Colt S/S 295
Colt S/S 340
Charger 295
Charger 400
Charger 530
Mustang 400
Mustang 530
34TT
44TT
Apache 338
Apache 396
Apache 433
Comanche 292
Cherokee 396
Cherokee 433
GT 292SS
GT 338SS
GT 433SS
Sport 25
Sport 30
American 305
American 40
American 40-E
Nitro 295
Nitro 340
Nitro 400
Nitro 440
Engine Size
339 cc
398 cc
436 cc
338 cc
438 cc
338 cc
438 cc
650 cc
175 cc
244 cc
294 cc
294 cc
335 cc
294 cc
398 cc
530 cc
398 cc
530 cc
398 cc
436 cc
338 cc
396 cc
433 cc
292 cc
396 cc
433 cc
292 cc
338 cc
433 cc
295 cc
340 cc
440 cc
440 cc
295 S cc
340 S cc
400 S cc
440 S cc
HP
25
30
36
36
43
36
43
55
12
20
22
23
25
22
30
42
30
42
32
40
25
28
33
21
28
33
29
34
43
25
30
40
40
N/A
N/A
N/A
40
Maximum
RPM
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
6500
6500
5500
5500
5500
5500
5500
5500
6500
6500
6500
6800
6800
6600
6600
7300
7300
7300
7200
Weight
375
375
375
365
365
380
380
385
286
300
330
325
330
390
400
410
453
463
420
420
320
320
320
295
335
335
320
320
320
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
410
Retail
Price
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
800
N/A
N/A
N/A
1199
1250
1569
1599
1769
1199
1399
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
995
1095
1245
1345
1395
1150
1250
1350
1450
Noise2
Level, dBA
80.4
N/A
83
80.4
83.5
80.4
82.6
83.2
79.5
82.2
81.7
81
81.1
79
80.5
83.5
81
83
79.9
81
81.5
82.5
82.7
81.3
82
82.5
81.5
83.5
83.8
80.9
82
N/A
83.8
83.8
82.6
82.1
82.6
83.7
B-5
-------
Manufacturer
Scorpion
Ski-Doo,
Sno-Jet
Speedway
Model
Stinger 290
Stinger 290 ET
Stinger 340
Stingerette
Super Stingerette
Super Stinger 400 RV
Super Stinger 400 TK
Super Stinger 440
Elan 250
Elan 250E
Elan 250T
Elan 250SS
Olympique 300
Ol/mpique 340
Olympique 340E
Olympique 400E
Olympique 440
Skandic 335
Nordic 640ER
T'NT SOOT
T'NT 340
T'NT 440
Alpine 440R
Alpine 440ER
Alpine 640ER
Valmont 440R
Valmont 440ER
Star Jet 292
Star Jet 338
Star Jet 433
SST 295
SST340
SST 440
Whisper Jet
340 Blue Max -FA3
440 Blue Max -FA
650 Blue Max -FA
Engine Size
290 cc
290 cc
339 cc
290 cc
339 cc
398 cc
398 cc
428 cc
246 cc
246 cc
247 cc
247 cc
299 cc
339 cc
339 cc
398 cc
436 cc
334 cc
293 cc
339 cc
436 cc
436 cc
436 cc
436 cc
436 cc
292Ycc
338Y cc
433Y cc
295S cc
340Scc
440Scc
440Ycc
340 cc
436 cc
650 cc
HP
22
22
26
22
26
33
40
42
12
12
16
22
15
23
23
27
28
20
23
28
28
28
28
28
28
19
24
30
27
32
38
30
34
61
90
Maximum
RPM
6500
6500
6000
6500
6000
6500
6800
6800
6000
6000
6000
6500
6000
6000
6000
6000
6500
6000
6000
6500
6500
6500
6500
6500
6500
5500
5500
5500
6500
6500
6500
5500
8500
8500
8500
Weight
316
311
325
316
325
358
358
386
265
301
270
280
338
360
360
400
373
N/A
495
375
390
405
548
584
610
506
540
328
350
350
328
350
355
408
330
346
370
Retail
Price
795
N/A
895
1045
N/A
1195
1195
1295
795
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
1150
N/A
N/A
N/A
N/A
N/A
N/A
859
999
1129
1049
1149
1299
1299
1500
1600
1850
Noise2
Level ,dBA
82.7
82.7
83.8
82.7
83.8
82.3
82.3
83.1
82
82
N/A
N/A
82
79
79
80.8
81
N/A
81.5
79.3
82
82
78.3
78.3
81.8
78.3
78.3
80.2
79
79.5
80.1
80.9
80.7
77.9
83.1
84
N/A
B-6
-------
Manufacturer
Suzuki
Yamaha
Model
292 Nomad
340 Nomad
XR-400
XR-440
SL 292 C
SL 338D
SL 433B
EL 433B
GP292B
GP 338
GP 433B
GP643B
SW 433C
EW 433C
EW 643B
Engine Size
292 cc
336 cc
395 cc
432 cc
292 cc
338 cc
433 cc
433 cc
292 cc
338 cc
433 cc
643 cc
433 cc
433 cc
643 cc
HP
20
26
33
36
20
24
30
30
27
32
30
50
30
30
42
Maximum
RPM
6000
5500
6000
6000
5500
5500
5500
5500
6000
6000
5500
6000
5500
5500
5500
Weight
362
370
377
388
337
363
365
400
337
358
365
425
392
431
462
Retail
Price
750
850
950
1050
850
950
1045
1195
950
1095
1250
1495
1195
1295
1595
Noise2
Level ,dBA
82
81.5
81.6
81.8
81.3
N/A
79.1
79
81.6
82
81.7
82
79.4
79.3
81.9
Reprinted from Invitation to Snowmobiling Magazine, October - November 1972 with per-
mission from Ms Sally Wimer. Noise data from New York State Office of Parks and
Recreation.
A
Noise levels measured in accordance with SAE Recommended Practice J192.
o
FA denotes Free Air.
B-7
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APPENDIX C
SAE Recommended Practice for Exterior Sound Level
for Snowmobiles
C-l
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UNO
SEA
AIM
SPACE
SOCIETY OF AUTOMOTIVE ENGINEERS, INC. • TWO PENNSYLVANIA PLAZA • NEW YORK. NEW YORK 10001
.
U ... ,-.5?u Ji, ~.. ,^-
w M,
© SOCIETY OF AUTOMOTIVE ENGINEERS. INC. 1970. THIS REPORT IS SCHEDULED FOR THE 1971 SAE HANDBOOK.
EXTERIOR SOUND LEVEL
FOR SNOWMOBILES-SAE J192
SAE Recommended Practice
Rqnrt of Vrhick S.u»4 U«l GnAnillM .pprovnl Slumber WTO.
7. Introduction— This SAE Recommended Practice establishes the
maximum exterior *ound level (or snowmobiles anil describes the test
procedure, environment, and instrumentation for determining this
sound level.
2. Sound Leitl Limit— The sound level produced by a new mow-
mobile shall not exceed 82
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EXTERIOR SOUND LEVEL FOR SNOWMOBILES
6.3 Instrument manufacturer'* specifications for orlentition of the
microphone relative to the tource of tound and the location of the
observer relative to the meter ihould be adhered to.
6A Measurement* thall be made only when wind velocity it below
\2 inph
6.5 Insirumcnl manufacturer's recommended calibration practice
<>t I lie iiisiuimenfs ihould be made at appropriate timei. Field calibra-
tion Oumlil be made immediately before and after each complete test.
fr'iihri an external calibrator or internal calibration means is accept-
.iblc (in liclil n«c. provided that external calibration is accomplished
iinmc
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APPENDIX D
State Snowmobile Noise Legislation: 1972
State
Colorado
Connecticut
Iowa
Massachusetts
Michigan
Minnesota
Montana
New Hampshire
New Mexico
New York
Ohio
Oregon
Rhode Island
Utah
Vermont
Washington
Wisconsin
Effective Date
(for machines
made after)
1-1-71
1-1-73
1-1-75
7-1-72
7-1-73
7-1-72
7-1-74
Present
2-1-72
6-70
2-72
6-30-72
7-1-73
7-1-78
7-1-83
7-1-72
6-72
6-75
6-78
1-1-73
1-4-73
6-1-72
6-1-74
9-20-71
9-1-72
1-4-73
7-1-72
6-75
Sound Level Requirements
Sound Level
(dBA)
86
84
85
86
82
82
73
86
82
86
82
85
82
73
70
86
82
78
73
82
82
82
73
82
82
82
82
78
Distance
from Source
(feet)
50
50
50
50
50
50
50
50
50
50
50
15
50
50
50
50
50
50
50
Not Specified
100
50
50
50
50
100
50
50
Compiled by International Snowmobile Industry Assoc. and reprinted with per-
mission of Sound and Vibration. The original list as it appeared in the May '73
issue has been corrected to reflect the recent change in the New York State law.
D-l
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BIBLIOGRAPHfC DATA
SHEET
1. Report No.
L'port No.
550/9-74-003-A
3. Recipient's Accession No.
5. Report Date
June 1974
4. Title and Subtitle .
Control of Snowmobile Noise, Volume 1, Technology
& Cost Information
6.
7. Author(s)
Bruce A. Davy, Ben H. Sharp
8. Performing Organization Re;'.
No.
9. Performing Organization Name and Address
Wyle Laboratories
10. Project/Task/Work Unit No.
11. Contract/Grant No.
68-01-1537
12. Sponsoring Organization Name and Address
Environmental Protection Agency
Office of Noise Abatement and Control
Crystal Mall #2, 1921 Jefferson Davis Highway
Ar.-Mngi-.nn, Virginia 2Q460
13. Type of Report & Period
Covered
Final (Vol. 1)
14.
15. Supplementary Notes
6. Abstracts
This document contains information useful for the development of
noise emission standards for snowmobiles. Topics covered include in-
formation on snowmobile construction, noise characteristics of models
currently on the market, and noise reduction techniques and costs
necessary to achieve specified noise levels.
'7, Key Words and Document Analysis. 17a. Descriptors
Recreational vehicle noise
Recreational vehicle noise control
Snowmobile noise
Snowmobile noise control
Costs of noise reduction
17b. Identificrs/Open-Ended Terms
17c. COSATI Tie Id/Croup
-t Availability Statement
Limited supply available at ONAC
Virginia 20460
Available at NTIS
Arlington,
19. Security Class (This
Report) v
UNCLASSIFIED *
20. Security Class (This
Page Y
UNCLASSIFIED A
21- No. of Pages
22. Price
NTIS-3S UO-701
USCOMM-DC 40329-PH
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