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Walker Valley Scottish Trials/poker run
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[QUOTE="fishhead, post: 588676, member: 18565"] Under current MNA rules you are allowed 2 retests before a DQ. Walker was not an NMA event so it's the the clubs choice how they enforce the sound limits pursuant to their NMA charter requirements. They are required to enforce sound rules in order to keep their NMA Club status. Doug and I are going to pull the sound meter and equipment out and try to isolate the offending frequencies by conducting some tests. Once we know what frequencies are dominant and what the test criteria is we will have a good idea of things that would adversly affect test results. For example, a 100 cycle sound wave is 11ft long and will readily couple with objects to amplify the sound pressure with 2nd,3rd and 4th order harmonics. Flat surfaces at angles close to 90 degress and tighter are most efficient reflectors of sound energy. Longer waves tend to couple with objects more readily than short waves and they tend to travel much farther. You might have noticed that you can hear the four strokes from farther away than the 2 strokes when you're riding and that it's not always easy to tell if their in front of you or behind you. This is the unidirectional characteristic of the lower frequecy sound waves. The irony is that the same energy that is harnessed in the exhaust system to tune the exhaust for the desired power is whats causing the uproar once it gets outside the pipe. The manufactures have the most resources and recently have made some great strides in pipe/silencer design that have less compromise as Highbeam noted on his XR. Just a hint that a long turn 90 elbow on a WR/YZ will direct sound energy toward the ground where it will have a more difficult time coupling with other objects and reflections will be directed toward free air. ;) This might be worth a couple or three db. :thumb: That might help get those cheater bikes past the tech and keep the ground pounders happy. [/QUOTE]
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Who to Ride With, Where to Ride
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Walker Valley Scottish Trials/poker run
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