Jonala - It's not just sound tests at CA enduros that have this problem. Trying to accurately measure the decibel level in an area where sound can reflect off objects such as the ground, trees, grass, etc. is difficult. Also, how many decibels are produced by engine noise alone, vs. exhaust noise. Stand between the engine and the decibel meter next time. Those vibration tachs are another source of problems. They are not very precise instruments. The only thing a sound check does is to prevent the rider who never repacks their silencer, and is usually way over 110 decibels, from riding that event... maybe.