Mountain View, CA Noise Ordinances: Vehicle Noise (2026)

The County Noise Ordinance (Division B11, Chapter VIII) contains a dedicated section on motor vehicle noise limits (Section B11-155). For vehicles operated on public streets and highways, however, the controlling law is generally state law, which preempts local exhaust standards for on-road vehicles. California Vehicle Code Section 27150 requires every motor vehicle to be equipped with an adequate muffler in constant operation and properly maintained to prevent excessive or unusual noise, and prohibits cutouts, bypasses or similar devices. Vehicle Code Section 27151 prohibits modifying a vehicle's exhaust system in a manner that amplifies or increases noise beyond legal limits, and provides that for vehicles under 6,000 pounds gross vehicle weight (other than motorcycles), a sound level of 95 dBA or less - when tested per the most current SAE International standard - complies with the section. Operating a vehicle with an illegally modified exhaust is a citable offense. Off-road and stationary vehicle noise on private property within the unincorporated County can additionally fall under the County's exterior noise limits and prohibited-acts provisions. Enforcement of on-road vehicle noise is typically by the Santa Clara County Sheriff or CHP, while the Department of Environmental Health handles property-line noise complaints.