Mariposa County, CA Noise Ordinances: Vehicle Noise (2026)

Mariposa County has not adopted a vehicle-noise ordinance, so motor-vehicle noise on public roads in the unincorporated county is controlled by the California Vehicle Code, enforced by the Mariposa County Sheriff and the California Highway Patrol. 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 exhaust cutouts or bypass devices. Section 27151 bars modifying an exhaust system to amplify or increase noise beyond legal limits; for vehicles under 6,000 pounds gross weight (other than motorcycles), a sound level of 95 dBA or less complies with the test standard. Section 27007 prohibits operating a sound amplification system that can be heard outside the vehicle from 50 or more feet while the vehicle is operated on a highway. The General Plan Noise Element specifically identifies motor-vehicle noise and 'off-road vehicles and recreational uses' as chief noise sources, noting that during summer months 'motorcycles use mountain roads and trails for recreational travel' and that 'noise from these vehicles can extend for miles in quieter mountain areas.' Even so, the county itself sets no decibel limit; loud exhausts, off-road vehicles and car stereos are addressed through these statewide rules, with extreme cases of malicious noise also reachable under Penal Code Section 415.