I used the AMA Supercross Sound Requirements:
C3 Test Site and Position of the Sound Meter
a. The sound levels will be measured with the sound meter/microphone fixed on a tripod, in the horizontal position, at the
rear of the motorcycle.
b. For the place and position of the motorcycle, ensure that there are no solid obstacles within 33 feet around the
microphone.
c. The sound meter will be positioned at a distance of 79 inches behind the motorcycle, with an angle of 45° away from
the centerline, on the exhaust side and at a height of 53 inches above the ground, with the sound meter level.
d. The 79 inch distance is measured from the point where the center of rear tire touches the ground.
e. It is preferred to make the tests on soft ground, not reverberating, i.e. grass or fine gravel.
Using Decibel Meter V2.2 on my iPhone placed on a tripod in grassy area positions appropriately I consistently got a max reading of 96 dB.
It should pass but I will try it again with some strategically placed steel wool to get it a few dB lower.
