Originally Posted by R1NGA
As I guess we all know, noise monitoring is not an exact science and so many things affect the final readings - weather conditions, position of the engine relative to the exhaust outlet, position of the vehicle relative to buildings, the meters themselves and indeed the operators. My Renault Spider (as I think I may have mentoined in a similar thread before) passed the Goodwood noise meter test one week at 96dB, yet failed the very next Saturday in the same place, with supposedly the same meter, but a different operator at 102dB. Bear in mind that a 3dB increase in reading is typically twice the sound pressure level, then you can see how ridiculous some testing processes are. I would never try to get anything other than a very rough idea of noise by using a different meter to the one the officials will use at the circuit. I have my own calibrated device and at 2/3's revs, 45-deg and 1/2m, readings vary from 97-102dB, so I can't even get consistency. However what I can do is put some track-day slip-on silencers onto the ends of (in my case) the G56 cans and these make a significant - and more importantly consistent - difference to the readings, with typically 3-4dB drop. I secure them with a clamp and also well hidden locating screw to keep even fussy Marshalls happy and always take them with me to a track event I do. Have only had to use them once, but well worth having in your back pocket as it were. Very little performance drop - certainly compared with being sent home thumbs

2.5" Slip-On Silencers

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Great and yes that is exactly the sort of thing I was looking for