Sound Checks at CA enduro's

[Jonala]

Yesterday I had entered the Cow Bell enduro. A sound check was required. I didn't ask what the limit was, but they did have riders go fix the mufflers.

What is interesting is that the USFS testing methods, are not repeatable.

I have a 01' XR250R, with a stock muffler/sparkarrester, with vortip type end. I used a calibrated sound meter to test my bike at home. My sound reading was 94 dB. RPM approx 2000.

When tested at the Polecat enduro the USFS got a reading of 96 dB.
Yesterday the USFS results were 94 dB.

They tested an XR400 without end piece. It read 98 dB. The ranger told the rider he passed today, but would not be allowed to ride next year with that reading. :eek:

 

[NVR FNSH]

John,
I wouldn't sweat a 2dB range. The background noise has a large impact on test. Did they use that little vibration tach? That's what I don't like. I want something I understand:think

Brian

 

[Jonala]

Originally posted by NVR FNSH
John,
Did they use that little vibration tach? That's what I don't like. I want something I understand:think

Brian

Yes, they used the vibration tach. What was interesting as I rolled into the sound check station, they passed my bike without even testing it. They saw I had the standard Honda muffler, and it " did sound" quite enough.

I asked them to take a reading.

 

[WoodsRider]

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.