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.