For purposes of this chapter, the following definitions shall apply:
A SCALE LEVEL (dB(A) Or dBA): Is expressed in decibels and shall be the sound pressure level which is frequency weighted in accordance with an A-weighting network.
dB(A) LEVEL: The total sound level of all noise, as measured with a sound level meter using the A-weighting network. The unit is the decibel.
DECIBEL (dB): A logarithmic unit of amplitude which denotes the ratio of two (2) quantities.
SOUND LEVEL METER: An instrument including a microphone, an amplifier, an output meter and frequency weighting networks for the measure of noise and sound pressure levels in a specified manner.
SOUND PRESSURE LEVEL (SPL Or Lp): Is expressed in decibels and shall be twenty (20) times the logarithm to the base ten (10) of the ratio of the effective sound pressure to the reference sound pressure. The effective sound pressure shall be the root-mean- square of the instantaneous sound pressure. The reference pressure shall be twenty (20) microneutrons per meter squared. (Prior code title 46, art. 23 § 290)
A. It is unlawful for any person to drive or move or for the owner to cause or knowingly permit to be driven or moved either a motor vehicle or combination of vehicles at any time in such a manner as to exceed the following noise limits for the category of motor vehicle shown in subsections A1 and A2 of this section. Noise shall be measured at a distance of twenty five feet (25') (7.5 m) from the near side of the nearest lane being monitored and at a height of at least four feet (4') (1.2 m).
1. Any motor vehicle with a manufacturer GVW rating of ten thousand (10,000) pounds or more or any combination of vehicle towed by such motor vehicles shall not emit a sound pressure level to exceed eighty eight (88) dB(A).
2. Any motor vehicle with a manufacturer GVW rating of ten thousand (10,000) pounds or less or any combination of motor vehicles towed by such motor vehicles shall not emit a sound pressure level to exceed eighty (80) dBA.
3. Subsections A1 and A2 of this section shall apply only to vehicles traveling on streets with a posted speed of forty (40) miles per hour or less.
B. This section applies to the total noise from a vehicle or combination of vehicles, and shall not be construed as limiting or precluding the enforcement of any other provisions of this title relating to motor vehicle mufflers for noise control.
C. No person shall sell or lease, or offer for sale or lease any motor vehicle of a type described above which exceeds the maximum decibel levels set forth above.
D. Any vehicle which is found not to be in conformity with this chapter and which is manufactured prior to January 1, 1974, may be exempted from the noise levels specified herein provided a good and sufficient showing can be made:
1. That it is mechanically impossible without major construction to modify such equipment so as to be in compliance; or
2. That to comply would cause irreparable harm or injury to the engine of said vehicle.
E. An exemption may be granted if the mayor, or his or her designated representative, shall be satisfied that a condition as provided above exists rendering compliance impossible, that the vehicle is equipped in all other respects so as to minimize to the maximum degree possible the objectionable noise, and that the noise thus emitted shall not be of such a nature as to necessitate its total prohibition.
F. This provision shall not apply to new equipment which, as manufactured, could have complied with the noise levels specified above, but which has been modified so as to no longer be in compliance. (Prior code title 46, art. 23 § 291)
Sound level measurement shall be made with a sound level meter using the A-weighting scale in accordance with those standards promulgated by the Society of Automotive Engineers, the American National Standards Institute, or any other procedure adopted and tested by the city departments charged with enforcing this chapter. (Prior code title 46, art. 23 § 292)
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