Law & Order

Montana Retains Fair and Objective Exhaust Noise Law

Montana legislation to repeal a SEMA-sponsored law enacted in 2007 that permits vehicles with modified exhaust systems that do not emit an excess of 95 decibels was tabled in committee. Under the repeal legislation, all exhaust system modifications that were subjectively determined by law enforcement to increase noise would have been illegal.

Under the current law, exhaust noise emissions are measured in accordance with SAE test standard J1169. Under the SAE standard, a sound meter is placed 20 inches from the exhaust outlet at a 45-degree angle, and the engine is revved to three-quarters of maximum rated horsepower. The highest decibel reading is then recorded.

Similar legislation to restrict exhaust system noise has been introduced this year in Connecticut and New Jersey. The Montana bill is effectively dead for the year.

For details, contact Steve McDonald at