DDK - Die Deutschen Klassiker

A friend running a GT3 Replica with approx 360bhp on tap with sports silencers was stooped from partaking in a track day recently for emitting 112dBa where the limit was 105dBA.

I used to be an acoustic expert and I lways thought that these tests would need to be pretty measured in terms of set up to get the correct result. His claim was when he passed previously the mic was set up behind the car in a methodical way, however when he failed they pushed the mic up into the exhaust. From my memory this would give a higher value due to air flow pressure and the fact teh noise has not been allowed to disperse, ie is more intense.

Has anyone got any comments on this. Is there a standard proceedure that all track day guys should follow??

Regards

Glenn

There is no standard measurement system on trackdays, although they should be using a repeatable method for race days:

Vehicles must be silenced to the requirements of the MSA Regulation [C(b)23] Chart 24 Section 'B’ (108dBA at ¾ rpm at 0.5m).

For track days each circuit has it's own method:

Castle Combe: All vehicles must comply to the strict noise limit of 100db(A), which is measured at ½ metre from the exhaust outlet at 4500rpm

Motorsport Vision: Each car is measured 0.5 meters away from the exhaust at a 45 degree angle when the engine is being held at ¾ of the maximum RPM
Brands Hatch: Indy Circuit (Daytime) - 105dB(A), Indy Circuit (Evening) - 102dB(A), GP Circuit 101dB(A)
Oulton Park: 105dB(A)
Cadwell Park: 105dB(A)
Snetterton: 105dB(A)
Bedford Autodrome: 101dB(A)

Many circuits also have driveby tests with separate limits. The marshals are under enormous pressure from local councils, they may seem like Nazis but every car must meet all these limits or the track will loose its licence and we will loose our trackdays.

Thanks Nick for the response