Current through Register 2024 Notice Reg. No. 38, September 20, 2024
(a) Mounting of Test Sample. Mechanical
sirens shall be mounted on a vehicle for open field testing. Electromechanical
sirens and electronic siren speaker assemblies shall be mounted on a test
fixture secured to a turntable in an anechoic chamber as follows:
(1) Height Above Turntable. The height,
measured from the lower edge of the siren stator housing of electromechanical
sirens or from the lower edge of the speaker bell of electronic sirens to the
face of the turntable, shall be 1.2 m ± 76 mm (4 ft ± 3
in.).
(2) Distance from Surface of
Test Area. Sirens shall be located as far from the walls of the anechoic
chamber as practicable.
(b) Power Supply. The electrical power supply
for testing electromechanical and electronic sirens shall be as follows:
(1) Electromechanical Sirens. The power
supply for the electromechanical siren under test shall be a battery of the
correct rated voltage with a cold cranking performance rating at -18° C
(0° F) of from 550 A to 620 A and a rated minimum reserve capacity at
26.7° C (80° F) of 140 min. The battery shall be at full charge and in
good condition at the start of the test.
(2) Electronic Sirens. The power supply for
electronic sirens shall be a well-filtered, voltage-regulated power source
meeting at least the requirements of SAE J823c, January 1975. The voltage
measured at the power supply output terminals with the siren operating shall be
as follows:
|
Rated voltage |
Test voltage for sound
level |
Test voltage for
wattage |
|
6 |
6.5 |
7.2 |
|
12 |
13.6 |
15.0 |
(c) Sound Level Meter Operation. The sound
level meter shall be operated in accordance with the instrument manufacturer's
instructions and as follows:
(1) Sound Level
Meter Setting. The sound level meter shall be set for the A-weighted network
and fast response.
(2) Octave Band
Analyzer. The octave band analyzer shall be operated to determine the octave
band containing the maximum sound output in each siren mode.
(3) Calibration Check. An external
calibration check shall be made before and after each period of use and at
intervals not exceeding 2 h when the sound measuring instrument is used for a
period longer than 2 h.
(4) Ambient
Sound. Measurements shall be made only when the A-weighted ambient sound level,
including wind effects and all other sound sources, is at least 10 dB(A) lower
than the sound level of the siren.
(d) Siren Operation. The mounted siren shall
be operated to determine the sound level output under each function at the
established test points as follows:
(1)
Electromechanical and electronic siren speakers shall be rotated from at least
50 deg left to 50 deg right of the center of the siren axis at a constant speed
during the siren operation.
(2)
Mechanical sirens shall be tested when mounted on a stationary vehicle and
operated at speeds equivalent to a road speed of 30 to 80 km/h (19 to 50 mph)
to determine maximum noise output straight ahead of the vehicle (the vehicle
may be mounted on rollers). The speed at which maximum sound level occurs shall
be continued while the microphone is moved from 50 deg left to 50 deg right of
the center of the vehicle axis.
1. Editorial
correction of NOTE (Register 81, No. 44).
Note: Authority cited: Section 26103, Vehicle Code.
Reference: Sections 26103 and 26104, Vehicle
Code.
