We here at ProCycle wanted to do an objective comparison of sound output from various exhaust systems. The test bike is a 2005 DR650. It's nearly stock with the factory BST carburetor, snorkel removed and a .030" washer under the needle clip. It has the OEM factory head pipe. All mufflers were tested on the same day in the same location with the same equipment. While the numbers may or may not be 'accurate' we are confident that our methods were consistent enough to give a valid comparison of noise levels between the mufflers tested. Decibel numbers are calculated on a logarithmic scale. A 3dB increase approximately doubles the sound energy. 5dB is a little more than 3 times the sound energy. A 10dB increase is a tenfold increase in sound energy.
We tested sound levels for 3 different situations.
First just sitting at idle. We positioned the sound meter in the same way as the J1287 stationary test but just measured sound at idle. The meter reading fluctuates up and down a couple of decibels. We recorded the closest average whole number between high and low readings.
Second, we replicated the USFS field sound test that the forest service rangers use as a field test. The details are reproduced below. The meter reading fluctuates up and down a couple of decibels. We recorded the closest average whole number between high and low readings.
Third, we put the test bike on the dyno and ran it wide open throttle from 60 to 80 mph in 5th gear. We positioned the sound meter 15 feet from the muffler tip at a 45 degree angle and recorded the highest reading on the meter.
The Results:
