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

The Sierra County Code does not contain a vehicle exhaust or muffler-noise ordinance. A search of the official county code for 'muffler' returns no matches, so the county relies on California state law, which is uniform statewide and enforceable by the Sierra County Sheriff and the California Highway Patrol. Under California Vehicle Code Section 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 Section 27151 makes it unlawful to modify an exhaust system in a way that amplifies or increases vehicle noise beyond the limits set by state law. State law also sets numeric sound limits for vehicles by type (the Vehicle Code provides, for example, that for many vehicles under 6,000 pounds an exhaust sound level of 95 dBA or less, tested to the applicable SAE standard, complies). The county code's only decibel figure is unrelated to passenger vehicles: SCC 8.04.260 limits solid-waste collection trucks to 75 decibels at 25 feet during stationary compaction. Drivers in unincorporated areas such as Downieville and Sierraville are therefore subject to state exhaust law rather than a separate county rule.