Both the EPA and the European standards call for an 80 dBA maximum sound level, but again the testing procedure is different — and in this case, significantly. In Europe, motorcycles must accelerate at full throttle from a set speed of no more than 30 mph in second gear, past a microphone. The microphone is set 25 feet away from the line of travel, such that the motorcycle passes perpendicular to the microphone 33 feet after acceleration starts. The EPA test procedure has the microphone further away at 50 feet, but the speed is such that the motorcycle passes the microphone in second gear at an rpm that (for motorcycles over 675cc) is 55 percent of maximum rated rpm — which refers to the rpm at which the engine makes peak power. Consider the difference: 30 mph in Europe compared to roughly 60 mph here in the USA. Even though the actual level is identical in the two standards, it’s much more difficult to meet that 80 dBA maximum here than in Europe.
http://www.sportrider.com/tech/motor...dards-ask-geek
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