| Different circuits use different methods, if they bother at all.
E.g. Goodwood did a static test last time I was there a few years ago, noise meter about half metre from the exhaust at angle of 45 degress then revs at whatever the tester thinks!!
Croft. Never seen a noide meter at the place, same at Cadwell.
If you are gonna do yer own testing there are loads of things that can affect readings, no least how open a area you test in, the wind direction etc, etc. Also rememebr that the DB scale is logarithmic,??? i.e three DB more is twice as loud, i.e. 103 DB is twice 100db.
Don't let this put you off, just search the web for circuit info, trackday companies websites or even call the circuit to ask what the limit and more importantly how they test.
Another caveat is that even if you "pass" the test with your own meter you could still "fail" at your chosen circuit due to the factors above, not least of which the circuit won't be using your meter!!
Noise is becoming an ever more sensitive issue, but it's not an exact science unfortunately as the open air is not the best laboratory to work in.
Ray  | 
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