TITLE 35: ENVIRONMENTAL PROTECTION
SUBTITLE H: NOISE
CHAPTER II: ENVIRONMENTAL PROTECTION AGENCY
PART 952
MEASUREMENT PROCEDURES FOR THE ENFORCEMENT
OF 35 ILL. ADM. CODE 902
SUBPART A: GENERAL PROVISIONS
Section
952.100 General Provisions
SUBPART B: INSTRUMENTATION
Section
952.110 Instrumentation
SUBPART C: MEASUREMENT OF NOISE EMISSIONS: HIGHWAY OPERATIONS
Section
952.120 Scope of this Subpart
952.121 Standard Site Characteristics
952.122 Restricted Site Characteristics
952.123 Ambient Conditions
952.124 Location and Operation of Sound Level Measurement System
952.125 Measurement Procedure
SUBPART D: MEASUREMENT OF NOISE EMISSIONS: STATIONARY TEST
Section
952.130 Scope of this Subpart
952.131 Site Characteristics
952.132 Ambient Conditions
952.133 Location and Operation of Sound Level Measurement System
952.134 Measurement Procedure
SUBPART E: MICROPHONE DISTANCE CORRECTION FACTORS
Section
952.140 Microphone Distance Correction Factors
SUBPART F: EXHAUST SYSTEMS AND TIRES
Section
952.150 Exhaust Systems and Tires
APPENDIX A STANDARD TEST SITE: HIGHWAY OPERATIONS
APPENDIX B RESTRICTED MEASURING SITE: HIGHWAY OPERATIONS
APPENDIX C RESTRICTED MEASURING SITE "D" AND "L" DETERMINATION FOR
REFLECTIVE SURFACE CORRECTION
APPENDIX D EXAMPLE OF D AND L DETERMINATION
APPENDIX E NOMOGRAPH TO DETERMINE CORRECTIONS FOR REFLECTIVE
SURFACES
APPENDIX F STANDARD TEST SITE: STATIONARY TEST
APPENDIX G EXAMPLE OF STANDARD TEST SITE: HIGHWAY OPERATIONS (60
FEET (18.3 m) DISTANCE BETWEEN MICROPHONE LOCATION AND
TARGET POINTS)
APPENDIX H EXAMPLE OF STANDARD TEST SITE: STATIONARY TEST (35 FEET
(10.7 m) DISTANCE BETWEEN MICROPHONE LOCATION AND
TARGET POINTS)
APPENDIX I PASSENGER CAR MICROPHONE POSITIONS
APPENDIX J OLD RULE NUMBERS REFERENCED
AUTHORITY: Implementing and authorized by Sections 25 and 27 of the Environmental
Protection Act (Ill. Rev. Stat. 1981, ch. 111 1/2, pars. 1025 and 1027) and 35 Ill. Adm. Code
900.103.
SOURCE: Adopted at 4 Ill. Reg. 19, p. 207, effective May 1, 1980; codified at 8 Ill. Reg.
18111.
SUBPART A: GENERAL PROVISIONS
Section 952.100 General Provisions
a) Introduction
This report describes procedures for inspection, surveillance and measurement of
motor vehicles and motor vehicle equipment to determine whether those motor
vehicles and motor vehicle equipment conform to the standards specified in 35 Ill.
Adm. Code 902 (old Part 3 of Chapter 8 of the Illinois Pollution Control Board
Rules and Regulations).
b) Definitions
"Hard test site": any test site having the ground surface covered with
concrete, asphalt, packed dirt, gravel or similar reflective material for
more than 1/2 the distance between the microphone target point and the
microphone location point.
"Soft test site": any test site having the ground surface covered with grass,
other ground cover or similar absorptive material for 1/2 or more of the
distance between the microphone target point and the microphone location
point.
"Ground cover": any of various low, dense-growing plants, such as ivy,
myrtle, low weeds or brush.
"Traffic railing": any longitudinal highway traffic barrier system installed
along the side or median of a highway. For the purpose of this report, a
traffic railing must have at least 35 percent of its vertical height, from the
ground surface to the top of the railing, open to free space in order to
qualify as an acceptable object within a noise measurement test site.
Further, for the purposes of this report, posts or other discrete supports
shall be ignored when ascertaining open free space.
"Relatively flat": when used to describe a noise measurement site means a
site which does not contain significant concave curvatures or slope
reversals that may result in the focusing of sound waves toward the
microphone location point.
c) Measurement Tolerances
1) Measurement tolerances will be allowed to take into account the effects of
the following factors:
A) The consensus standard practice of reporting field sound level
measurements to the nearest whole decibel (dB).
B) Variations resulting from commercial instrument tolerances.
C) Variations resulting from the topography of the noise measurement
site.
D) Variations resulting from atmospheric conditions such as wind,
temperature and atmospheric pressure.
E) Variations resulting from reflected sound from small objects
allowed within the test site.
F) The interpretation of the effects of the above cited factors by
enforcement personnel.
2) Measurement tolerances shall not exceed:
A) 1 dB for Type 1 sound level meters;
B) 2 dB for Type 2 and Type S sound level meters.
3) Measurement tolerances are to be added to the applicable sound level
limit.
SUBPART B: INSTRUMENTATION
Section 952.110 Instrumentation
a) Scope of this Subpart
This Subpart specifies criteria for sound level measurement systems which are
used to make the sound level measurements specified in Subparts C and D of
these measurement procedures.
b) Type of Measurement Systems Which May Be Used
The sound level measurement system must meet or exceed the requirements of
American National Standards Institute Specification for Sound Level Meters
(ANSI §1.4-1971), approved April 27, 1971, issued by the American National
Standards Institute throughout the applicable frequency range for either:
1) A Type 1 sound level meter;
2) A Type 2 sound level meter; or
3) A Type S sound level meter which has:
A) A-weighting frequency response;
B) Fast dynamic characteristics of its indicating instrument; and
C) A relative response level tolerance consistent with those of either a
Type 1 or Type 2 sound level meter, as specified in Section 2.1 of
ANSI §1.4-1971.
c) Calibration of Measurement Systems
1) A) The sound level measurement system must be calibrated and
appropriately adjusted at one or more frequencies in the range
from 250 to 1,000 Hertz (Hz) at the beginning of each series of
measurements and at intervals of 5-15 minutes thereafter, until it
has been determined that the sound level measurement system has
not significantly drifted from its calibrated level. Once this fact
has been established, calibrations may be made at intervals once
every hour. A significant drift shall be considered to have
occurred if a 0.3 dB or more excursion is noted from the system's
predetermined reference calibration level. In the case of systems
using displays with whole decibel increments, the operator may
visually judge when the 0.3 dB drift has been met or exceeded.
B) The sound level measurement system must be checked once every
twelve months by its manufacturer, a representative of its
manufacturer, or a person of equivalent special competence to
verify that its accuracy meets the manufacturer's design criteria.
2) An acoustical calibrator of the microphone coupler type designed for the
sound level measurement system in use shall be used to calibrate the
sound level measurement system in accordance with subsection (c)(1).
The calibration must meet or exceed the accuracy requirements specified
in Subsection 5.4.1 of the American National Standards Institute Standard
Methods for Measurements of Sound Pressure Levels, (ANSI §1.13-1971)
for field method measurements.
d) Windscreens
A properly installed windscreen, of the type recommended by the manufacturer of
the Sound Level Measurement System, shall be used during the time that noise
emission measurements are being taken, in order to minimize the wind generated
noise on the microphone and to protect the microphone from dust and other
airborne matter. The windscreen also reduces damage to the microphone in the
event the tripod is upset or the microphone is dropped.
SUBPART C: MEASUREMENT OF NOISE EMISSIONS: HIGHWAY OPERATIONS
Section 952.120 Scope of this Subpart
a) This Subpart specifies conditions and procedures for measurement of the sound
level generated by a motor vehicle engaged in a highway operation for the
purpose of ascertaining whether the motor vehicle conforms with 35 Ill. Adm.
Code 902.120(b)(1) and (b)(2), 902.121(b)(1) and (b)(2), 902.122(b)(1) and (b)(2)
and 902.123(c).
b) A "standard site" is a measurement site which conforms with the specifications
listed under Chapter 325.33 "Site Characteristics: highway operations" of
Subpart C of "Department of Transportation Bureau of Motor Carrier Safety
Regulations for Enforcement of Motor Carrier Emission Standards," as described
below in Section 952.121. A standard site must be utilized to determine
compliance with 35 Ill. Adm. Code 902.121: Standards Applicable to Motor
Vehicles with Gross Vehicle Weight (GVW) in Excess of 8,000 Pounds and 35
Ill. Adm Code 902.123: Exception for and Standards Applicable to Motor
Carriers Engaged in Interstate Commerce with Respect to Operations Regulated
Pursuant to the Federal Noise Control Act of 1972. A standard site may be
utilized to determine compliance with 35 Ill. Adm. Code 902.120: Standards
Applicable to All Passenger Cars and to Other Motor Vehicles with GVW of
8,000 Pounds or Less and 35 Ill. Adm. Code 902.122: Standards Applicable to
Motorcycles and Motor Driven Cycles.
c) 1) A "restricted site" is a measurement site at which:
A) The distance from the microphone to the center of the near lane of
travel is greater than 26 feet (7.9 meters (m)) or less than 100 feet
(30.2 m), or
B) The distance from the microphone target point to large reflecting
surfaces is less than the distance between the microphone and the
microphone target point, or
C) The distance from the microphone to large reflecting surfaces is
less than the distance between the microphone and the microphone
target point (See Appendix B).
2) A restricted site may be utilized to determine compliance with 35 Ill.
Adm. Code 902.120: Standards Applicable to All Passenger Cars and to
Other Motor Vehicles with GVW of 8,000 Pounds or Less and 35 Ill.
Adm. Code 902.122: Standards Applicable to Motorcycles and Motor
Driven Cycles.
Section 952.121 Standard Site Characteristics
a) Measurements shall be made at a test site which is adjacent to, and includes a
portion of, a traveled lane of a public highway. A microphone target point shall
be established on the centerline of the traveled lane of the highway, and a
microphone location point shall be established on the ground surface not less than
35 feet (10.7 m) or more than 83 feet (25.3 m) from the microphone target point
and on a line that is perpendicular to the centerline of the traveled lane of the
highway and that passes through the microphone target point. Within the test site
is a triangular measurement area. A plan view diagram of a standard test site is
shown in Appendix A. Measurements may be made at a test site having smaller
or greater dimensions in accordance with the following:
1) If the distance between the microphone location point and the microphone
target point is other than 50 feet (15.2 m), the test site must be an open site
with a radius from both points which is equal to the distance between the
microphone location point and the microphone target point.
2) Plan view diagrams of standard test sites are shown in Appendices G and
H. Appendix G illustrates a test site which has a 60 foot (18.3 m) distance
between the microphone location point and the microphone target point.
Appendix H illustrates a test site which has a 35 foot (10.7 m) distance
between the microphone location point and the microphone target point.
b) The measurement site must be an open site, essentially free of large sound
reflecting objects. However, the following objects may be within the
measurement site, including the triangular measurement area:
1) Small cylindrical objects such as fire hydrants or telephone or utility poles
located 3 feet (1 m) or more from the microphone.
2) Rural mailboxes located 3 feet (1 m) or more from the microphone.
3) One or more curbs having a vertical height of 1 foot (.3 m) or less.
c) The following objects may be within the test site if they are outside of the
triangular measurement area of the site:
1) Any vertical surface (such as a billboard), regardless of size, having a
lower edge more than 15 feet (4.6 m) higher than the surface of the
traveled lane of the highway.
2) Any uniformly smoooth sloping surface slanting away from the highway
(such as a rise in grade alongside the highway) with a slope that is less
than 45 degrees above the horizontal.
3) Any surface slanting away from the highway that is 45 degrees or more
and not more than 90 degrees above the horizontal, if all points on the
surface are more than 15 feet (4.6 m) above the surface of the traveled
lane of the highway.
d) 1) The surface of the ground within the triangular measurement area must be
relatively flat. If the site is determined to be "hard," the correction factor
specified below shall be applied to the sound level limits of 35 Ill. Adm.
Code 902.121 and 902.123.
2) When measurements are made upon a test site which is "hard," a
correction factor of 2 dB(A) shall be added to the sound level limits of 35
Ill. Adm. Code 902.121(b)(1), 902.121(b)(2) and 902.123(c).
e) The traveled lane of the highway within the test site must be dry, paved with
relatively smooth concrete or asphalt, and substantially free of:
1) Holes or other defects which would cause a motor vehicle to emit irregular
tire, body or chassis impact noise; and
2) Loose material, such as gravel or sand.
f) The traveled lane of the highway on which the microphone target point is situated
must not pass through a tunnel or underpass located within 200 feet (61 m) of that
point.
Section 952.122 Restricted Site Characteristics
a) Restricted measuring sites are those sites where sound reflecting surfaces are
close to either the microphone or the microphone target point as specified in
Section 952.120(c).
b) Measurements shall be made at a test site which is adjacent to, and includes a
portion of a traveled lane of a public highway. A microphone target point shall be
established on the centerline of the traveled lane of the highway and a
microphone location point shall be established on the ground surface not less than
26 feet (7.9 m) or more than 100 feet (30.2 m) from the microphone target point
and on a line that is perpendicular to the centerline of the traveled lane of the
highway and that passes through the microphone target point.
c) A sound reflecting surface is any building, signboard, hillside or similar object,
within the measurement site, that reflects sufficient sound to affect the sound level
readings obtained from passing vehicles. Such sound reflecting surfaces make
this site a restricted measurement site. Some sound reflecting surfaces require a
correction to the measured sound level.
1) Surfaces not requiring correction. The following surfaces and objects
within the measuring site do not require a correction factor:
A) Small cylindrical objects such as fire hydrants or telephone or
utility poles located 3 feet (1 m) or more from the microphone.
B) Rural mailboxes located 3 feet (1 m) or more from the microphone.
C) Traffic railings of any type of construction except solid concrete
barriers.
D) Chain-link fences or any vegetation such as bushes, shrubs, hedges
and grass.
E) One or more curbs having a vertical height of 1 foot (.3 m) or less.
F) The following objects may be within the measurement site if they
are outside of the triangular measurement area of the site:
i) Any vertical surface (such as a billboard), regardless of
size, having a lower edge more than 15 feet (4.6 m) higher
than the surface of the traveled lane of the highway.
ii) Any uniformly smooth sloping surface slanting away from
the highway (such as a rise in grade alongside the highway)
with a slope that is less than 45 degrees above the
horizontal.
iii) Any surface slanting away from the highway that is 45
degrees or more and not more than 90 degrees above the
horizontal, if all points on the surface are more than 15 feet
(4.6 m) above the surface of the traveled lane of the
highway.
2) Surfaces Requiring Correction. Sound level measurements may be made
with appropriate corrections when sound reflecting surfaces are within the
measuring site as shown in Appendix B. Measurements may be made
only when the sound reflecting surfaces are basically parallel to the lane of
travel.
A) A basically parallel surface may have irregularities or projections
of not more than 2 feet (.6 m) measured perpendicular to the lane
of travel, with the distance to the microphone line or vehicle path
measured from the closest point of the projection.
B) Sound reflecting surfaces not basically parallel to the lane of travel
shall be a minimum of 35 feet or B, whichever is greater, from the
microphone and microphone target point. (B is the distance
between the microphone and microphone target point as shown in
Appendix B.) This restriction does not apply to surfaces that are
perpendicular to the lane of travel and behind the parallel surface
for which corrections are made, such as a fence or the side walls of
a building.
C) Distance measurements from smooth embankments covered with
vegetation, concrete, asphalt, dirt or other relatively smooth cover
shall be made from the point where the slope begins to exceed 45
degrees above horizontal. Measurements from non-smooth
embankments shall be made from the point where the irregularity
begins.
3) Correction Factors for Sound Reflecting Surfaces. Correction factors to
be added to the applicable sound level limits when there are sound
reflecting surfaces within the restricted measurement site shall be
determined as follows:
A) Reflecting Surfaces. Sites with sound reflecting surfaces basically
parallel to the vehicle path within the measuring area shown in
Appendix B may be used by measuring the distances shown in
Appendix B and adding the correction factor obtained from the
nomogram in Appendix E to the applicable sound level limit.
B) Measuring Distances to Determine Correction. Measurement "D"
is the shortest distance between the centerline of the lane of travel
and the reflecting surface located on the opposite side of the lane
of travel from the measurement location (see Appendices B, C and
D). Measurement "L" is the shortest distance between a line
parallel to the lane of travel passing through the microphone and
the reflecting surface behind the measurement location (see
Appendices B, C and D).
C) Determining Correction Factor. Locate the points on the left and
right scales of Appendix E corresponding to the distances "D" and
"L" in Appendices B and C. Place a straight edge across the
nomogram so that it connects the two points. The point where the
straight edge intersects the center axis indicates the correction
factor to be added to the applicable sound level limit.
4) Correction Factor for a Microphone Mounted on a Passenger Car. A
correction factor of 1dB shall be added to the appliable sound level limit
when a microphone is mounted on a passenger car.
Section 952.123 Ambient Conditions
a) Sound
1) The ambient A-weighted sound level at the microphone location point
shall be measured, in the absence of motor vehicle noise emanating from
within the clear zone, with fast meter response using a sound level
measurement system that conforms to these procedures.
2) The measured ambient level of non-motor vehicle sound must be
10 dB(A) or more below that level which corresponds to the maximum
permissible sound level reading which is applicable at the test site at the
time of testing. The maximum permissible sound level reading is the
sound level limit appropriate for each vehicle type, plus the site
corrections.
b) Wind. Noise measurements may only be made if the measured wind velocity is
12 miles per hour (mph) (19.3 kilometers per hour (kph)) or less. The wind
velocity at the test site shall be measured at the beginning of each series of noise
measurements and at intervals of 5-15 minutes thereafter until it has been
established that the wind velocity is essentially constant. Once that fact has been
established, wind velocity measurements may be made at intervals of once every
hour. Gust wind measurements of up to 20 mph (33.2 kph) are allowed, although
sound level measurements may not be taken at these times.
c) Precipitation. Sound level measurements are prohibited under any condition of
precipitation, however, measurements may be made with snow on the ground.
The ground surface within the measurement area must be free of standing water.
Section 952.124 Location and Operation of Sound Level Measurement System
a) Microphone Position
1) Unless mounted on a passenger car, the microphone of a sound level
measurement system that conforms to this report shall be located at a
height of not less than 2 feet (.6 m) nor more than 6 feet (1.8 m) above the
plane of the roadway surface and not less than 3.5 feet (1.1 m) above the
surface on which the microphone stands. The preferred microphone
height on flat terrain is 4 feet (1.2 m).
A) When the sound level measurement system is hand-held or is
otherwise monitored by a person located near its microphone, the
holder must orient himself relative to the highway in a manner
consistent with the recommendation of the manufacturer of the
sound level measurement system.
B) In no case shall the meter holder or observer be closer than 2 feet
(.6 m) from the system's microphone, nor shall he locate himself
between the microphone and the vehicle being measured.
2) If mounted on a passenger car, the microphone of a sound level
measurement system that conforms to this report shall be located in the
following manner:
A) The microphone shall be located 1 foot (.3 m) plus or minus 1/2
foot (.15 m) above the roof of the passenger car (see Appendix I,
Figure 1).
B) The microphone shall be located in the vertical plane of the edge
of the roof on the driver's side of the passenger car plus or minus
1/2 foot (.15 m) (see Appendix I, Figure 2).
C) The microphone shall be located between the front and back edges
of the roof of the passenger car.
D) The passenger car shall be positioned either perpendicular or
parallel to the lane of travel.
b) The microphone of the sound level measurement system shall be oriented toward
the traveled lane of the highway at the microphone target point at an angle that is
consistent with the recommendation of the system's manufacturer. If the
manufacturer of the system does not recommend an angle of orientation for its
microphone, the microphone shall be oriented toward the highway at an angle of
not less than 70 degrees and not more than perpendicular to the horizontal plane
of the traveled lane of the highway at the microphone target point.
c) The sound level measurement system shall be set to the A-weighting network and
"fast" meter response mode.
Section 952.125 Measurement Procedure
a) In accordance with this Subpart, a measurement shall be made of the sound level
generated by a motor vehicle operating through the measurement area on the
traveled lane of the highway within the test site, regardless of the highway grade,
load, acceleration or deceleration.
b) The sound level generated by the motor vehicle is the highest reading observed on
the sound level measurement system as the vehicle passes through the
measurement area, corrected, when appropriate, in accordance with these
measurement procedures. The sound level of the vehicle being measured must be
observed to rise at least 6 dB(A) before the maximum sound level occurs and to
fall at least 6 dB(A) after the maximum sound level occurs in order to be
considered a valid sound level reading.
SUBPART D: MEASUREMENT OF NOISE EMISSIONS: STATIONARY TEST
Section 952.130 Scope of this Subpart
a) This Subpart specifies conditions and procedures for measuring the sound level
generated by a vehicle when the vehicle's engine is rapidly accelerated from idle
to governed speed at wide open throttle with the vehicle stationary, its
transmission in neutral, and its clutch engaged, for the purpose of ascertaining
whether the motor vehicle conforms with 35 Ill. Adm. Code 902.121(c) or
902.123(d).
b) This Subpart applies only to a motor vehicle with GVW in excess of 8,000
pounds that is equipped with an engine speed governor.
c) Tests conducted in accordance with this Subpart may be made on either side of
the vehicle.
Section 952.131 Site Characteristics
a) The motor vehicle to be tested shall be parked on the test site. A microphone
target point shall be established on the ground surface of the site on the centerline
of the lane in which the motor vehicle is parked at a point that is within 3 feet (.9
m) of the longitudinal position of the vehicle's exhaust system outlet(s). A
microphone location point shall be established on the ground surface not less than
35 feet (10.7 m) and not more than 83 feet (25.3 m) from the microphone target
point. Within the test site is a triangular measurement area. A plan view diagram
of a standard stationary test site, is shown in Appendix F.
b) The test site must be an open site, essentially free of large sound-reflecting
objects. However, the following objects may be within the test site, including the
triangular measurement area:
1) Small cylindrical objects such as fire hydrants or telephone or utility poles
located 3 feet (1 m) or more from the microphone.
2) Rural mailboxes located 3 feet (1 m) or more from the microphone.
3) Traffic railings of any type of construction except solid concrete barriers.
4) Chain-link fences or any vegetation such as bushes, shrubs, hedges and
grass.
5) One or more curbs having a height of 1 foot (.3 m) or less.
c) The following objects may be within the test site if they are outside of the
triangular measurement area of the site:
1) Any vertical surface, regardless of size (such as a billboard), having a
lower edge more than 15 feet (4.6 m) above the ground.
2) Any uniformly smooth surface slanting away from the vehicle with a slope
that is less than 45 degrees above the horizontal.
3) Any surface slanting away from the vehicle that is 45 degrees or more and
not more than 90 degrees above the horizontal, if all points on the surface
are more than 15 feet (4.6 m) above the surface of the ground in the test
site.
d) 1) The surface of the ground within the measurement area must be relatively
flat. The site shall be a "hard" site. However, if the site is determined to
be "soft," the correction factor specified below shall be subtracted from
the applicable sound level limit.
2) When measurements are made upon a test site which is "soft," a correction
factor of 2 dB(A) shall be subtracted from the sound level limits of 35 Ill.
Adm. Code 902.121(c) and 902.123(d).
Section 952.132 Ambient Conditions
a) Sound
1) The ambient A-weighted sound level at the microphone location point
shall be measured, in the absence of motor vehicle noise eminating from
within the clear zone, with fast meter response using a sound level
measurement system that conforms to these procedures.
2) The measured ambient level must be 10 dB(A) or more below that level
which corresponds to the maximum permissible sound level reading which
is applicable at the test site at the time of testing. The maximum
permissible sound level reading is the sound level limit plus the necessary
site corrections.
b) Wind. Noise measurements may only be made if the measured wind velocity is
12 mph (19.3 kph) or less. The wind velocity at the test site shall be measured at
the beginning of each series of noise measurements and at intervals of 5-15
minutes thereafter until it has been established that the wind velocity is essentially
constant. Once this fact has been established, wind velocity measurements may
be made at intervals of once every hour. Gust wind measurements of up to 20
mph (33.2 kph) are allowed, although sound level measurements may not be
taken at these times.
c) Precipitation. Measurements are prohibited under any conditions of precipitation,
however, measurements may be made with snow on the ground. The ground
within the measurement area must be free of standing water.
Section 952.133 Location and Operation of Sound Level Measurement System
a) The microphone of a sound level measurement system that conforms to these
measurement procedures shall be located at a height of not less than 2 feet (.6 m)
nor more than 6 feet (1.8 m) above the plane of the roadway surface and not less
than 3.5 feet (1.1 m) above the surface on which the microphone stands. The
preferred microphone height on flat terrain is 4 feet (1.2 m).
b) When the sound level measurement system is hand-held or otherwise monitored
by a person located near its microphone, the holder must orient himself relative to
the highway in a manner consistent with the recommendation of the manufacturer
of the sound level measurement system. In no case shall the holder or observer be
closer than 2 feet (.6 m) from the system's microphone, nor shall he locate himself
between the microphone and the vehicle being measured.
c) The microphone of the sound level measurement system shall be oriented toward
the vehicle at an angle that is consistent with the recommendation of the system's
manufacturer. If the manufacturer of the system does not recommend an angle of
orientation for its microphone, the microphone shall be oriented at an angle of not
less than 70 degrees and not more than perpendicular to the horizontal plane of
the test site at the microphone target point.
d) The sound level measurement system shall be set to the A-weighting network and
"fast" meter response mode.
Section 952.134 Measurement Procedure
In accordance with this Subpart, a measurement shall be made of the sound level generated by a
stationary motor vehicle as follows:
a) Park the motor vehicle on the test site as specified in this Subpart. If the motor
vehicle is a combination (articulated) vehicle, park the combination so that the
longitudinal centerlines of the towing vehicle and the towed vehicle or vehicles
are in substantial alignment.
b) Turn off all auxiliary equipment which is installed on the motor vehicle and
which is designed to operate under normal conditions only when the vehicle is
operating at a speed of 5 mph (8 kph) or less. Examples of such equipment
include cranes, asphalt spreaders, liquid or slurry pumps, auxiliary air
compressors, welders and trash compactors.
c) If the motor vehicle's engine radiator fan drive is equipped with a clutch or similar
device that automatically either reduces the rotational speed of the fan or
completely disengages the fan from its power source in response to reduced
engine cooling loads, park the vehicle before testing with its engine running at
high idle or any other speed the operator may choose, for sufficient time but not
more than 10 minutes, to permit the engine radiator fan to automatically
disengage when the vehicle's noise emissions are measured under stationary test.
d) With the motor vehicle's transmission in neutral and its clutch engaged, rapidly
accelerate the vehicle's engine from idle to its maximum governed speed with
wide open throttle. Return the engine's speed to idle.
e) Observe the maximum reading on the sound level measurement system during the
time the procedures specified in subsection (d) are followed. Record that reading,
if the reading has not been influenced by extraneous noise sources such as motor
vehicles operating on adjacent raodways.
f) Repeat the procedures specified in subsections (d) and (e) until the first two
maximum sound level readings that are within 2 dB(A) of each other are
recorded. Numerically average those two maximum sound level readings.
g) The average reading, obtained in accordance with subsection (f), is the sound
level generated by the motor veicle for the purpose of determining whether it
conforms with the equivalent sound level limits of 35 Ill. Adm. Code 902.121(c)
or 902.123(d).
SUBPART E: MICROPHONE DISTANCE CORRECTION FACTORS
Section 952.140 Microphone Distance Correction Factors
a) Scope of this Subpart
1) This Subpart specifies correction factors which are added to the applicable
sound level limit to be compared with the measured sound level generated
by a motor vehicle.
2) The purpose of adding a correction factor is to determine equivalent sound
level limits for distances between the microphone target point and the
microphone location point other than 50 feet (15.2 m).
b) Microphone Distance Correction Factors
If the distance between the microphone location point and the microphone target
point is other than 50 feet (15.2 m), the equivalent sound level limit shall be
determined by adding the correction factor specified in the following table to the
applicable sound level limit:
DISTANCE CORRECTION FACTORS
If the distance between the
The value (dB(A)) to be
microphone location point
added to the applicable
and the microphone target
sound level limit is:
point is:
26 feet (7.9 m) or more but
+7
less than 29 feet (8.8 m)
29 feet (8.8 m) or more but
+6
less than 32 feet (9.8 m)
32 feet (9.8 m) or more but
+5
less than 35 feet (10.7 m)
35 feet (10.7 m) or more but
+3
less than 39 feet (11.9 m)
39 feet (10.7 m) or more but
+2
less than 43 feet (13.1 m)
43 feet (13.1 m) or more but
+1
less than 48 feet (14.6 m)
48 feet (14.6 m) or more but
0
less than 58 feet (17.7 m)
58 feet (17.7 m) or more but
-1
less than 70 feet (21.3 m)
70 feet (21.3 m) or more but
-2
less than 83 feet (25.3 m)
83 feet (25.3 m) or more but
-3
less than 100 feet (30.2 m)
c) Application of Correction Factors
If two or more correction factors apply to a sound level limit they are applied
cumulatively.
SUBPART F: EXHAUST SYSTEMS AND TIRES
Section 952.150 Exhaust Systems and Tires
a) Exhaust Systems
A motor vehicle does not conform to the visual exhaust system inspection
requirements of 35 Ill. Adm. Code 902.101 and 902.123(b), if inspection of the
exhaust system of the motor vehicle discloses that the system:
1) Has a defect which adversely affects sound reduction, such as exhaust gas
leaks or alteration or deterioration of muffler elements (small traces of
soot or flexible exhaust pipe sections shall not constitute a violation of 35
Ill. Adm. Code 902.101 and 902.123(b);
2) Is not equipped with either a muffler or other noise dissipation device; or
3) Is equipped with a cut-out, by-pass or similar device, unless such device is
designed as an exhaust gas driven cargo unloading system.
b) Tires. A motor vehicle does not conform to the visual tire inspection
requirements, 35 Ill. Adm. Code 902.102 and 902.123(b), if inspection of any tire
on which the vehicle is operating discloses that the tire has a tread pattern
composed primarily of cavities in the tread (excluding sipes and local chunking)
which are not vented by grooves to the tire shoulder or circumferentially to each
other around the tire.