UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON. D.C. 20460
NOISE TEST
DEVELOPMENT & VALIDATION
PROGRAM
FOR
LIGHT VEHICLES
EXECUTIVE SUMMARY
— PROGRAM PLAN —
MARCH 1977
STANDARDS AND REGULATIONS DIVISION
OFFICE OF NOISE ABATEMENT AND CONTROL
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NOISE TEST
DEVELOPMENT & VALIDATION PROGRAM
FOR LIGHT VEHICLES
In considering whether light vehicle regulatory action is
requisite to the protection of the public health and welfare from
noise from such vehicles, it is necessary to define a suitable
method for measuring light vehicle noise emissions. Several methods
have been developed and accepted for motor vehicle noise measurement.
These methodologies as applicable to automobiles and light trucks are
generally considered to be unsuitable for potential regulatory purposes
since they are not representative of the way in which these vehicles are
typically operated and hence their noise impact on the community is not
appropriately identified. With this realization, the U. S. EPA has
embarked on a program to develop and validate a noise measurement pro-
cedure which is more consistent with the noise generated by light motor
vehicles as they operate in the U. S. urban environment. A general
requirement of such a procedure is that it be applicable for all
categories of light motor vehicles and is technically and economically
reasonable to implement.
The light vehicle noise measurement procedure currently in general
use in the United States and local community regulation of vehicle noise
is the SAE J986a procedure. This procedure specifies the measurement
of noise for full-throttle vehicle operation at speeds in excess of 30
mph. From existing vehicle operation surveys, it is known that full-
throttle acceleration is not a typical mode of operation for most light
vehicles, and hence is responsible for only a part of the noise impact
received by the urban community. Further, vehicles judged to be equally
noisy by the SAE J986a procedure do not necessarily contribute equally
to community noise. It has also been observed that values of noise
reduction achieved by many engineering treatments and measured under
full-throttle conditions are not exhibited in other, less severe
operating conditions.
Because the SAE J986a procedure does not fulfill the requirements
for providing a method for reasonably assessing community noise due to
light vehicles, a more representative procedure is deemed necessary by
the U. S. EPA.
Since high noise levels are associated with the vehicle accelera-
tion mode, this type of operation will be assessed in particular, by the
EPA. To aid in specifying typical vehicle operation in this mode, there
are several sources of data available which supply information on the low
speed acceleration mode. This includes three sources of published infor-
mation as well as limited kinematic measurements that have been made by
EPA of light vehicles accelerating away from traffic lights. Each of
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the published sources has been examined in detail by EPA and its
contractors and none has been found to be adequate for determining
typical vehicle operating modes in urban environments. Nevertheless,
the measurements made by EPA can be compared to the published studies
to afford some preliminary conclusions.
Taking these three sources of information together, it appears
that two preliminary conclusions can reasonably be made. The first
conclusion is that light vehicles accelerate approximately linearly
between about 5 mph and 25 mph on typical urban streets by the local
speed limit. The second conclusion is that light vehicles accelerate
at a rate of about .15g. However, for vehicles at stop signs, or lead
vehicles at a traffic light, the uninfluenced rate may be somewhat
higher, possibly .17g to .20g.
In order to establish a light vehicle noise measurement procedure
which could reasonably be used as the basis for regulation, EPA is
currently conducting a program to develop and validate such a procedure.
This procedure will involve some form of low speed acceleration or
"urban acceleration." In the course of the program approximately 100
vehicles will be tested. In the first phase, about 15 selected vehicles
will be tested extensively to aid in the development and validation of
the test procedure. The second phase will establish a noise emission
data base using the EPA developed test procedure. A summary outline of
the program is attached which describes specific elements of the test
development and data base phase.
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SUMMARY OUTLINE NOISE TEST
DEVELOPMENT & VALIDATION PROGRAM
FOR LIGHT VEHICLES
INTRODUCTION:
This is a 6 task program designed to develop a noise measurement
test procedure and establish a noise emission data base using that pro-
cedure for light vehicles.
TASK 1; Evaluate Light Vehicle Noise Methodology
The purpose of this task is to evaluate a light vehicle low
speed acceleration noise measurement procedure. The evaluation will
include consideration of:
• Representation of typical vehicle operation as defined
by existing data.
• Biasing toward specific vehicle types.
• Application to differing vehicle configurations partic-
ularly regarding application to automatic and manual
transmission vehicles.
• Test practicality including
ease of performance
time of performance
instrumentation requirements
• Anticipated test repeatability
• Alternative test procedures including
constant acceleration
constant partial throttle
maximum throttle
quasi-constant throttle
constant speed
combinations of the above
• Relation to other existing test procedures, particularly
the SAE J986a.
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A number of vehicles of differing characteristics will be
examined for performance with various test procedures. Particular
attention in this examination will be placed on the occurrence of
shift points for manual and automatic transmission vehicles and the
sensitivity of the procedure on shift points.
TASK 2; Test Vehicles Identification and Acquisition
The objectives of this task are to identify the full range
of 1976 and 1977 model automobiles and light trucks, domestic and
foreign, prepare a list of parameters that might relate to noise
emissions, and to obtain approximately 100 of these vehicles for the
purpose of noise emission testing.
The parameters to be listed for each vehicle will include
the following:
o Make, series, engine type, engine displacement, curb
weight, carburetion, BMP, net torque, maximum rpm,
transmission, vehicle speed as a function of engine
speed in 1st and 2nd gears, and sales.
The listing will also include parameters obtained from the above
information, such as power-to-weight ratio, rated torque to rated power
ratio, etc., as required.
Approximately 100 vehicles will be acquired for testing purposes.
Tune-up specifications will be obtained for each vehicle. The approximate
mix of vehicles will be included:
o 15 subcompact, 10 compact, 10 mid-size, 20 large, 5 two
seater, 5 small station wagons, 5 mid-size wagons, 5
large-station wagons, 5 small pick-up trucks, and 10
vans/special purpose trucks.
The vehicles selected for testing will have accumulated more than 500
miles but not more than 15,000 miles. They will be obtained from rental
agencies, leasing agencies, local dealers or manufacturers as available.
TASK 3; Prepare Data Acquisition and Reduction System
The purpose of this task is to define the test parameters to be
measured and to develop and prepare a suitable instrumentation system for
data acquisition and reduction.
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The parameters to be monitored continuously during the test
are as follows:
• Exterior noise level (8 locations)
• Interior noise level
• Engine speed
• Vehicle distance
• Vehicle speed
• Vehicle acceleration
• Engine manifold pressure
• Wind speed and direction
• Temperature
• Relative humidity
A telemetry system will be employed to transmit the vehicle
data to the control room. Data will be acquired and stored by three
separate systems as follows:
A real-time visual display on a chart recorder of
all parameters - to provide on immediate check that
all systems are working properly and an approximate
indication of the value of each parameters as a func-
tion of time.
A permanent analog record of each parameter on
magnetic tape - to allow for future spectral analysis,
etc.
A permanent digitized record of each parameter on
magnetic tape - to allow for immediate analysis of
the data by plotting any one parameter against any
other at the completion of each test run. Both plot-
ting and printing capability will be provided, as well
as the capablity to search the data from all vehicle
runs and determine trends with respect to any desired
parameter.
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TASK 4; Preliminary Light Vehicle Noise Emission Test
The purpose of this task is the experimental evaluation and
development of a light vehicle low speed acceleration test procedure.
This testing will involve noise measurements of approximately 15 test
vehicles operating according to the proposed procedure as well as other
conditions includng cruise, coast, SAE J986a, and modifications of the
low speed acceleration procedure. Specific considerations in the pre-
liminary testing in regard to the proposed test procedure will include:
• Specification of vehicle shift points particularly
for manual transmission vehicles.
• Evaluation of alternative test procedures.
• Directivity of the vehicle in performance along the
test section.
• Proper placement of microphones along the test
section.
• Run-to-run variation in sound level and vehicle
performance under the proposed test procedure.
• Variation attributable to changes in ambient environ-
mental conditions.
• Instrumentation requirements for proper specifica-
tion of vehicle operation as required by the test
procedure.
The parameters listed in Task 3 will be simultaneously processed
by computer to provide immediate data plots and allow for daily analysis
of the results.
TASK 5; Light Vehicle Noise Emission Tests
The purpose of this task is to obtain a noise level data base
for light vehicles performing in accordance with the proposed low speed
acceleration test procedure. This testing will include approximately
100 vehicles. Pending the results of preliminary testing under Task 4,
it is anticipated that each vehicle will be tested under the following
operating conditions:
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• Low speed acceleration (proposed test procedure)
• Coast
• Cruise
• Full throttle acceleration including SAE J986a
procedure
Multiple runs under each operating condition will be performed as
required.
Using the instrumentation system developed in Task 3, the
measurements for each vehicle in this test program will include:
• Exterior sound level (8 channels)
• Interior A-weighted sound level
• Vehicle position in the test section
• Vehicle velocity
• Vehicle acceleration
• Engine speed
• Engine manifold pressure
The on-site computer will also be used to generate plots and tables of
the relevant test data.
The data for each vehicle will be reviewed for consistency and
if anomalies occur, thorough and immediate analysis will be performed
to ascertain the cause of the observed behavior.
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TASK 6: Analyze Test Data
The purpose of this task is to provide analysis of the test data
generated in Tasks 4 and 5. This analysis will be performed at least
weekly. The analysis will be directed at the determination of:
Measured and calculated parameters or groups of
parameters which correlate with vehicle noise production.
Trends in the data set exhibited by differing types of
vehicles.
Physical principles underlying observed trends in the
data set.
Statistical descriptions of the data including expected
sound levels and variances for various grouping of the
vehicles.
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