A new test procedure by the Society of Automotive Engineers recommends allowing motorcycle exhaust pipe noise levels from 92 dBA to 100 dBA and describes a procedure for determining decibel levels.
The J2825 Measurement of Exhaust Sound Pressure Levels of Stationary On-Highway Motorcycles requires that sound be measured with a hand-held calibrated meter at a distance of 50.8 cm, with the meter held at a 45-degree angle.
It recommends setting limits at 92 dBA for idling motorcycles, 100 dBA for three- and four-cylinder motorcycles at higher engine speeds or increasing rpm levels, and 96 dBA for motorcycles with fewer than three cylinders or more than four at predetermined or increasing rpm levels.
The test recommendations were issued in May and are supported by the American Motorcyclist Association. The SAE conducted a large study of on-road motorcycles before coming up with the recommendations, which also cover the type of instruments to be used, structure of test sites, test conditions, and other elements.