Aftermarket Exhaust Firms Face Vague Regulations

Feb 7, 2014

Aftermarket exhaust manufacturers, retailers and wholesalers are all affected by exhaust noise laws, but the unclear nature of many of the regulations make them difficult to decipher, according to Gary Stamberger, technical training manager at MagnaFlow.

The Hawaii state legislature recently introduced a house bill (H.B. 2209) that would require official inspection stations to test vehicles to determine if their exhaust systems “emit noise noticeably greater than that emitted by the vehicle as equipped from the factory.” Hawaii is one of more than 15 states that have introduced or passed a law prohibiting modified mufflers that emit more noise than the original factory-installed muffler, according to BIPAC, a nonprofit dedicated to increasing political effectiveness of the business community. However, the majority of laws don’t indicate legal decibel level or how vehicles should be tested.

“In most cases, they do leave it very subjective, loosely written,” Stamberger said. “There are state regulations and local regulations, but it often comes right down to the community where they may have some type of noise-reduction law in place or something along those lines.”

Motor vehicle regulations typically maximize exhaust noise level at 80 to 95 decibels and the federal level standard is 95 decibels, but many local ordinances leave it up to the discretion of local police officers. Because Hawaii’s H.B. 2209 provides no test by which vehicle exhausts could be tested or provide inspection stations with decibel readings for factory-installed exhaust systems, it might force inspectors to fail vehicles for a violation of an unspecified test, according to the SEMA Action Network (SAN).

Seven states, including California, Michigan, Nevada and Oregon, have passed objective methods for measure exhaust noise, while more than two dozen other states have passed more vague laws prohibiting the use of a muffler that emits “excessive or unusual” noise.

Photo courtesy of the SEMA Action Network.

Stamberger recommends that shops and customers stay educated on laws and check with local law enforcement for specific guidelines. Although he isn’t completely sure why the laws are so unclear, he guesses that equipping law enforcement officers with equipment and resources to measure decibel levels might be a financial burden on some communities.

“They would have to have specifications for the factory decibel level, equipment to measure the decibel level and they would have to prove that the decibel level of the aftermarket exhaust is louder than the factory,” Stamberger said.

Stamberger notes that changing the tone of the exhaust with an aftermarket system does not necessarily increase the decibel level, a fact that isn’t address by many laws, including Hawaii’s pending regulation. All of MagnaFlow’s performance exhaust systems meet the federal level standard of 95 decibels, and the company makes an effort to supply its customers with as much information as it can about exhaust laws, he said.

To read MagnaFlow’s statement regarding exhaust laws, visit

To read more about Hawaii’s exhaust law, visit