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From Motocross Action

http://www.motocrossactionmag.com/ME2/dirmod.asp?sid=&nm=&type=news&mod=News&mid=9A02E3B96F2A415ABC72CB5F516B4C10&tier=3&nid=E38BF0D00CD1460283049D29E0254B99

HOW LOUD IS A BIKE IN REALITY

In a recent test of mufflers, Pro Circuit built a 90 dB muffler, 96 dB muffler, 99 db muffler and 102 dB muffler. They tested all four mufflers with their sound test equipment and on their dyno. Once they had established all the criteria, they took all four mufflers out and did drive-by sound tests as full throttle. Surprise, all four mufflers were within 1 dB of each other. They all ranged from 112 dB to 113 dB. Pro Circuit’s conclusion? Testing sound at 4800 rpm, when the bikes are ridden closer to 11,000 rpm, is a total waste of time. And, the inherent problem with AMA sound testing is that it doesn’t actually test anything even closely related to the real world. A 250F is tested at 5800 rpm, but revs to 13,500 rpm. A 450F is tested at 4800 rpm, but revs to 12,000 rpm. Why is the AMA wasting so much time testing something that only happens when the bikes are idling on the starting line?

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From Motocross Action

http://www.motocrossactionmag.com/ME2/dirmod.asp?sid=&nm=&type=news&mod=News&mid=9A02E3B96F2A415ABC72CB5F516B4C10&tier=3&nid=E38BF0D00CD1460283049D29E0254B99

HOW LOUD IS A BIKE IN REALITY

In a recent test of mufflers, Pro Circuit built a 90 dB muffler, 96 dB muffler, 99 db muffler and 102 dB muffler. They tested all four mufflers with their sound test equipment and on their dyno. Once they had established all the criteria, they took all four mufflers out and did drive-by sound tests as full throttle. Surprise, all four mufflers were within 1 dB of each other. They all ranged from 112 dB to 113 dB. Pro Circuit’s conclusion? Testing sound at 4800 rpm, when the bikes are ridden closer to 11,000 rpm, is a total waste of time. And, the inherent problem with AMA sound testing is that it doesn’t actually test anything even closely related to the real world. A 250F is tested at 5800 rpm, but revs to 13,500 rpm. A 450F is tested at 4800 rpm, but revs to 12,000 rpm. Why is the AMA wasting so much time testing something that only happens when the bikes are idling on the starting line?

Half the rated full rpm range is the standard to test at. Why would PC test on a dyno??? Makes absolutely no sense, inside, walls for sound to bounce off, etc.

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