Nevada Administrative Code
Chapter 484D - Equipment and Size, Weight and Load of Vehicles
EQUIPMENT OF VEHICLES
Noise Emission Standards
Section 484D.185 - Noise emission measurements: Vehicle noise level

1. The sound level reading for determining compliance with NAC 484D.150 must be the highest reading obtained as the vehicle or combination of vehicles passes through the measuring site on the highway. Sound level readings must be recorded on vehicles which are in lanes of travel with centerlines at or beyond 50 feet and which produce noise levels exceeding the regulatory limits.

2. The sound level readings for determining compliance of new motor vehicles with NAC 484D.155 must be obtained by making at least four measurements for each side of the vehicle. Sufficient preliminary runs must be made to familiarize the driver with the operation of the vehicle and to stabilize the engine operating condition. The A-weighted sound level for each side is the average of the two highest readings on that side which are within 2 dB of each other. The noise level reported for the vehicle must be the sound level of the loudest side of the vehicle. Obvious vehicle malfunction nullifies the test.

3. Tolerances are necessary due to unavoidable variations in test site, vehicle operation, test equipment, temperature and wind gradients, and inherent differences in nominally identical vehicles. Vehicles specified in NAC 484D.150 may not be considered in violation unless they exceed the limits in that section by more than 2 dB. New vehicles must be designed to comply with the limits in NAC 484D.155 at the time of manufacture to ensure that the vehicles will not exceed those limits plus a 2 dB tolerance when tested by an enforcement agency.