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

A search of the Modoc County Code (codified through Ord. No. 325-A, Jan. 2026) found no chapter setting decibel limits for cars, motorcycles or trucks, no engine-brake or 'Jake brake' prohibition, and no local muffler standard for highway vehicles. On-road vehicle noise in the unincorporated county is therefore controlled by California state law, which is uniform statewide and preempts most local exhaust rules. California Vehicle Code Section 27150 requires every motor vehicle to have an adequate muffler in constant operation to prevent excessive or unusual noise, and prohibits cutouts and bypasses. Section 27151 makes it unlawful to modify an exhaust system to amplify or increase noise beyond legal limits; for vehicles under 6,000 pounds (other than motorcycles), 95 dBA or less, tested to the applicable SAE standard, complies. These rules are enforced by the Modoc County Sheriff and the California Highway Patrol. The one vehicle-type noise rule in the county code is for boats: Section 8.12.030(D) makes it unlawful to operate a motorboat on any county lake or reservoir unless the motor is equipped with a muffler or other silencing device that deadens the noise of escaping gases, except for underwater exhausts without a cutout and authorized racing. There is no broader on-road noise chapter.