You need to know the stroke of your motor (that's why you sometimes see 50.6 or similar written on head fins in texta), then there's a table which calibrates what revs you should run your engine at when being tested.
The MA fun police are issued with another small device which is triggered by the resonance of your motor to indicate when it reaches the required rev range for your readings to be taken.
BUT...
If you repack your mufflers, don't race round the pits, don't fire up your bike and rev it outside track curfew hours, and especially DON'T keep bringing up noise as an issue on forums like this, after a while the fun police will forget about it, and go and pick on something else....
