Current through Register 2024 Notice Reg. No. 38, September 20, 2024
Noise from vehicles in use shall be measured as
follows:
(a) Microphone Location. The
sound level measuring microphone shall be in one of the following locations:
(1) Primary Location. The microphone shall be
located at a height not less than 0.6 m (2 ft), not more than 1.8 m (6 ft)
above the plane of the roadway surface, and not less than 1.1 m (3.5 ft) above
the surface upon which the microphone stands. The preferred microphone height
on a flat surface is 1.2 m (4 ft).
(2) Secondary Location. The microphone may be
mounted on a boom affixed to the exterior of a passenger vehicle or the sound
level meter with microphone attached may be held by a person sitting astride an
open motorcycle.
(A) When the microphone boom
is used, the microphone shall be located 0.41 m ± 7.6 cm (16 in.
± 3 in.) above the highest point of the vehicle within an area bounded
by the windshield, the tops of left and right front windows, and the rear of
the driver's seat. The vehicle upon which the microphone is mounted shall be
positioned so that its longitudinal axis is perpendicular to the center of the
lane of travel. The height of the microphone above the plane of the roadway
surface shall not exceed 2.4 m (8 ft). A correction factor of -2dB(A) shall be
applied to the recorded sound level.
(B) When the sound level meter with
microphone attached is held by a person sitting astride an open motorcycle, the
motorcycle shall be positioned parallel to the center of the lane of travel.
The microphone shall be pointed toward the traffic and project beyond the
windshield if the motorcycle is so equipped. The microphone shall be within the
height requirements specified in preceding subsection (a)(1). A correction
factor of -1dB(A) shall be applied to the recorded sound
level.
(b)
Distance from Microphone to Target Point. The horizontal distance from the
microphone to the microphone target point shall normally be 15.2 m (50 ft) but
may range from 7.9 m (26 ft) to 30.2 m (99 ft) if the following correction
factors are used:
|
Distance from microphone to center of lane
of travel |
Sound level correction factor,
dB(A)* |
|
7.9-8.8 m (26-29 ft)
n........................... |
.......................... -6 |
|
8.8-9.8 m (29-32
ft)........................... |
.......................... -5 |
|
9.8-10.7 m (32-35
ft)........................... |
.......................... -4 |
|
10.7-11.9 m (35-39
ft)........................... |
.......................... -3 |
|
11.9-13.1 m (39-43
ft)........................... |
.......................... -2 |
|
13.1-14.6 m (43-48
ft)........................... |
.......................... -1 |
|
14.6-17.7 m (48-58
ft)........................... |
.......................... 0 |
|
17.7-21.3 m (58-70
ft)........................... |
.......................... +1 |
|
21.3-25.3 m (70-83
ft)........................... |
.......................... +2 |
|
25.3-30.2 m (83-99 ft)
**.......................... |
.......................... +3 |
* If the distance from microphone to center of lane of
travel falls on the midpoint between distance ranges given in the table, the
larger correction factor shall be used.
** These distances are not applicable to measurements of
heavy trucks with a gross vehicle weight rating (GVWR) of over 4,537 kg (10,000
lb) operated by motor carriers engaged in interstate commerce and governed by
the Federal Bureau of Motor Carrier Safety regulations.
(c) Measuring Sites. Sites for measuring
sound from vehicles in use shall meet the following requirements:
(1) Standard Sites. As shown in Figure 1,
standard measuring sites shall have the microphone 15.2 m (50 ft) from the lane
of travel, be free of sound-reflecting surfaces within a 15.2 m (50 ft) radius
of the microphone and of the microphone target point, and be approximately
level.
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(2) Modified Sites. Modified measuring sites
shall meet the specifications shown in Figure 1, except the dimensions may
range from 7.9 to 30.2 m (26 to 99 ft). The radii of the minimum clear area
shall be the distance between the microphone and the microphone target point.
Sound level readings taken at such sites shall be corrected as provided in
preceding subsection (b). The site shall be free of large sound-reflecting
objects, with the following exceptions:
(A)
The following objects may be anywhere within the site:
1. Small cylindrical objects such as fire
hydrants or utility poles.
2. Rural
mailboxes.
3. Traffic railings of
any type of construction except solid concrete barriers.
4. Curbs having a vertical height of not more
than 0.3 m (1 ft).
5. Small bushes,
shrubs, hedges, or trees.
(B) The following objects may be within the
measuring site but outside the triangular measuring area:
1. Any vertical surface (such as a billboard)
regardless of size with a lower edge more than 4.6 m (15 ft) above the roadway
surface.
2. Any uniformly smooth,
sloping surface rising away from the highway with a slope less than 45 deg
above horizontal.
3. Any surface
rising away from the highway that is 45 deg or more and not more than 90 deg
above horizontal if all points on the surface are more than 4.6 m (15 ft) above
the roadway.
4. Any object on the
side of the vehicle path opposite the microphone with a width measured parallel
to the vehicle path not exceeding 1.0 m (3.1 ft) regardless of height, and not
slanting toward the roadway. If objects exceeding 1.0 m (3.1 ft) in width (such
as parked vehicles) are on the side of the vehicle path opposite the
microphone, a correction factor of -2 dB(A) shall be applied to the recorded
sound level.
(d) Moving Vehicles. Noise from vehicles in
use shall be measured as the vehicle passes through the measuring site.
Measurements shall be made under the conditions under which the vehicle is
operating, regardless of vehicle load, grade, acceleration, or deceleration.
(1) The traveled lane of the roadway within
the measuring site shall be dry and paved with relatively smooth concrete or
asphalt.
(2) The traveled lane
shall be free of holes or other defects that would cause a vehicle to emit
irregular tire, body, or chassis impact noise and shall be free of significant
areas of loose material such as sand or gravel.
(3) The microphone target point shall not be
within 61 m (200 ft) of a tunnel or underpass through which the vehicle
travels.
(4) The sound level must
rise at least 6 dB(A) to the maximum level and fall at least 6 dB(A) below the
maximum level as the vehicle passes to ensure that noise from other vehicles
does not interfere with the sound of the vehicle being
measured.
(e) Stationary
Heavy Motor Vehicles. Noise measurements of stationary in-use motor vehicles
with a gross vehicle weight rating of more than 4,537 kg (10,000 lb) and
equipped with an engine speed governor shall be made in accordance with the
following procedures:
(1) Vehicle Location:
The vehicle shall be parked on a measuring site meeting the requirements of
preceding subsection (c). The centerline of the vehicle shall be on the center
of the lane of travel as shown in Figure 1. The vehicle shall be positioned so
the exhaust system outlet is within 1.0 m (3.3 ft) of the microphone target
point measured along the center of the lane of travel.
(2) Auxiliary Equipment. Auxiliary equipment
used only when the vehicle is stationary or operating at a speed of 8 km/h (5
mph) or less shall be turned off. Such equipment includes but is not limited to
cranes, asphalt spreaders, ditch diggers, slurry pumps, auxiliary air
compressors, welders, and trash compactors.
(3) Engine Cooling Fans. If the engine
cooling fan automatically disengages or reduces speed in response to reduced
engine cooling loads, the engine shall be run at high idle, or any other speed
the operator may choose, for sufficient time but not more than 10 min to permit
the fan to operate at reduced speed during the noise test.
(4) Engine Operation. With the transmission
in neutral and the clutch engaged, the engine shall be rapidly accelerated from
idle to its maximum governed speed with wide open throttle. After the engine
speed has stabilized, the engine shall be returned to idle. This procedure
shall be repeated until the maximum sound level readings are within 2 dB(A) of
each other, disregarding unrelated peaks due to extraneous ambient
sound.
(5) Sound Level Measurement.
The recorded sound level for the stationary vehicle shall be the numerical
average of the highest 2 or more readings within 2 dB(A) of each other. This
level shall not exceed 88 dB(A) on a measurement site with concrete, asphalt,
packed dirt, gravel or similar reflective material for more than one-half the
distance between the microphone and the microphone target point. The level
shall not exceed 86 dB(A) on a measuring site with grass, other ground cover,
or similar absorptive material for more than one-half the distance from the
microphone target point.
1. Repealer
and new section filed 7-1-83; effective thirtieth day thereafter (Register 83,
No. 27).
2. Amendment of subsection (a) filed 11-20-84; effective
thirtieth day thereafter (Register 84, No. 47).
Note: Authority cited and Reference: Sections 23130,
23130.5 and 27207, Vehicle Code.
