The American Motorcyclist Association is proposing a plan to reduce sound levels at all its professional and amateur Supercross and Motocross racing events.
"Responsible sound management is an important part of the AMA's strategic planning regarding the safety and health of both our competitors and race fans," said AMA chief executive officer Patricia DiPietro. "These measured reductions in the sound limits for closed-course competition at both the professional and amateur levels will not only make race courses safer and more enjoyable for competitors and fans alike, but they will improve the standing of our events among non-race fans who are nevertheless impacted by our sound policies."
Currently, motorcycles in closed-course AMA-sanctioned motorcycle competition must meet sound limits of 99 decibels (on the "A" scale), measured at a distance of 20 inches from motorcycle's exhaust outlet. The proposed plan calls for reducing the allowable standard to 98 dB(A) for 2008, 97 dB(A) for 2009 and 96dB(A) for 2010. The present European sound limit for off-road motorcycles is already 96dB.
The current sound testing procedure uses the SAE J1287 stationary sound test, developed by the Society of Automotive Engineers: With the engine warm and the transmission in neutral, engine revolutions per minute (rpm) are brought up to the specified test speed (306,000m divided by the stroke in millimetres) and a sound reading is taken. The sound level is measured 20 inches from the exhaust outlet, with the sensor held parallel to the ground and at a 45-degree angle to the exhaust centreline.
"Sound is every motorcyclist's responsibility, because excessive sound impacts every motorcyclist, from competitor to street rider," DiPietro said. "It's important that we continue to move forward and improve in this important area."