Both cars and motorcycles with aftermarket exhausts or exhaust pipes typically catch the attention of law enforcement agents seeking to clamp down on overly loud systems in communities and neighborhoods. Many times the effort is boosted by homeowner and business complaints. However, a certain amount of noise is legal in many jurisdictions, regardless of personal opinions.
Sound carries by the change of air waves. Exhausts are designed to dampen the engine sound created from combustion. If there was no exhaust pipe, engines would be too loud for normal hearing within 50 feet. However, sport exhausts create additional pressure by design, which then creates louder engine cycle sounds.
The Environmental Protection Agency sets standards for exhaust manufacturers, which is seen by a product stamp on exhausts. However, it is states that frequently legislate noise limits on upper tolerances of exhaust sound. Some restrict pipes to what the EPA has approved. Others follow arbitrary noise limits passed in law regardless of the circumstances.
California enacted an arbitrary limit capped at 95 decibels with the engine running at between 3,000 and 5,000 RPM. Because evaluation of the noise produced can be hard to prove on the street, the law allows for the vehicle owner to have the exhaust tested for a definitive noise certification if cited.
