question about measuring exhaust decibals

[fastrider450r]

i was wondering how the GNCC people measure the decibals of exhaust pipes. Like how far away do they hold the decibal meter and is it at idle or rev.
thanks

[prepracing]

they hold the meter 1 ft away ( I think thats what it was ) from the back of your pipe, and another guys holds your throttle at a constant rpm just a little above an idle for a few seconds. But they get several complaints that their method is not very accurate. Atleast thats how it was done the last time mine got checked.

[Toadz400]

When some friends of mine went riding up in northern Wisconsin they held it a few inches from the end of the pipe and held the throttle at 1/2 throttle.

So basically every quad they did measured illegal, a stock Z400 was rated at 97 decibels.

this test is administered at a 20 inch distance from the exhaust pipe at half the quads rated rpm.

[JDiablo]

it is also suppose to be mesured at a angle towards the exhaust with it a lil bit above idle

[jiffers]

here in the uk they hold the meter 20" away and at a 45 degree angle and at about 1/2 revs

[fastrider450r]

is that how that exhaust companies measure the sound?