Contra Costa County, CA Noise Ordinances: Vehicle Noise (2026)

California Vehicle Code § 27150(a): "Every motor vehicle equipped with an internal combustion engine and subject to registration shall at all times be equipped with an adequate muffler in constant operation and properly maintained to prevent any excessive or unusual noise, and no muffler or exhaust system shall be equipped with a cutout, bypass, or similar device." California Vehicle Code § 27151(a) prohibits modifying a vehicle's exhaust system to amplify or increase the noise emitted by the vehicle above that emitted by the muffler originally installed, in violation of Section 27150 or applicable noise limits. For motor vehicles with a manufacturer's gross vehicle weight rating of less than 6,000 pounds, other than motorcycles, a sound level of 95 dbA or less, when tested in accordance with the most current SAE International standard, complies with this section. California Vehicle Code § 27007: "No driver of a vehicle shall operate, or permit the operation of, any sound amplification system which can be heard outside the vehicle from 50 or more feet when the vehicle is being operated upon a highway, unless that system is being operated to request assistance or warn of a hazardous situation." In unincorporated Contra Costa County, the Sheriff's Office enforces these California Vehicle Code provisions; there is no separate county muffler ordinance.