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About sound testing....
Stan Gale In order to meet local regulations, your bike will be sound tested and must meet 96DBa or less before you're allowed to ride at Sun Valley MX. If you're bike doesn't pass in its stock condition, there are simple bolt-on solutions at several nearby motorcycle shops. How the testing's done: 1) We'll use the standard "stationary sound test" (SAE J1287 - Motorcycle Industry Council and Society of Automive Engineers).
2) We'll use the latest Specification Model Test RPM Data to determine testing RPM for any bike sound tested by Sun Valley MX.
3) The sound meter used is calibrated.
4) Procedure - SAE J1287 summary:
Preparation
A 20-inch long string is attached to the front of the sound level meter for the stationary sound test. Allow the sound level meter to come to the same temperature as the surroundings. Set sound level meter to the slow dynamic response and the A-weighting network.
Test Site
No one should be within 10 feet of the bike other than the rider, the sound meter operator, an assistant to hold the front of the bike (if needed) and one other person directly behind the sound meter operator (if needed). The test area should be a flat, open surface free of large sound-reflecting surfaces within 16 feet (5 meters), such as parked vehicles, buildings, signs, and hillsides.
The surface should be free of loose soil, or grass higher than 6 inches (150 millimeters). The ambient sound level (including wind effects) at the site shall be at least 10 dB lower than the sound level of the vehicles tested. Always use a windscreen under windy conditions. The stationary test procedure should not be conducted if the wind speed is 20 mph (9m/s) or higher. If it is necessary to test in higher winds, position the vehicle so the wind direction is parallel to the normal direction of travel of the bike. Also, do not attempt sound level measurement when it is raining or snowing.
Measuring the Bike's Sound
Make sure the engine is warmed up and the transmission is in neutral. Have the rider sit on the motorcycle with both feet on the ground, or on the footrests, so that the vehicle is vertical and stationary.
Hold the sound meter at a 45-degree angle to the exhaust centerline (the normal line of travel) Parallel to the ground 20 inches to the rear of the exhaust outlet at the same height as the exhaust outlet.
Determine the test RPM for the make, model, and year of vehicle.
Set the vibrating reed tachometer to the test RPM, or attach an electric tachometer.
Have the rider or assistant hold the vibrating reed tachometer against any solid part of the bike, or have the rider or assistant read the meter of the electric tachometer.
Have the rider slowly increase the engine speed to the test RPM. Have the rider or assistant signal when the correct RPM is held.
Read the sound level meter when the correct RPM is held. Bike's that read 96DBa or less are allowed to ride. |
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