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

Loud cars, trucks, and motorcycles are the one noise topic where a clear, enforceable rule applies in unincorporated Siskiyou County, but it comes from the State of California rather than a county ordinance. The County itself has no noise ordinance (confirmed by a CPUC environmental review). California Vehicle Code Section 27150 requires that every motor vehicle subject to registration be equipped at all times with an adequate muffler in constant operation and properly maintained to prevent any excessive or unusual noise, and it prohibits mufflers or exhaust systems fitted with a cutout, bypass, or similar device. California Vehicle Code Section 27151 separately prohibits modifying a vehicle's exhaust system in a manner that amplifies or increases the noise so the vehicle no longer complies with Section 27150 or exceeds the noise limits set for that vehicle type. State law sets a passing sound level of 95 dBA for vehicles under 6,000 pounds (other than motorcycles) tested under the applicable procedure. Because these are statewide standards, they apply uniformly on roads and highways throughout unincorporated Siskiyou County and are enforced by the California Highway Patrol and the Siskiyou County Sheriff's Office. The County does not add its own decibel rule on top of the Vehicle Code. Off-highway and recreational vehicle noise is likewise governed by state Vehicle Code spark-arrester and equipment provisions rather than a county ordinance.