I had my S3, which has side pipes noise tested at Thruxton this week, they have a 90db noise limit, was very surprised to hit 86db at 4000rpm, it sounds much louder than that!
I really wouldn't read too much into that as noise testing procedures like this are hopelessly open to variance and massively unreliable. What they do allow however is for venues to disallow obviously noisy cars on track days where they would upset the neighbours - it's a neat way to show a black & white reason why a car can't run.
I did 2 track days at Goodwood the other year in the same car (Renaultsport Spider), just 2 weeks apart. Pretty much the same weather, nothing had changed yet first test measured 96dB (4,500rpm, 0.5m, 45deg angle) and the second 106dB. Given that the logarithmic scale means that +3dB is broadly twice the volume, that's one heck of an increase. Different bloke measured using the same device on the same settings (I asked for proof that they were doing it correctly). Maybe the wind was in the other direction of there were more reflections off other cars in the vicinity, but either way it's an imprecise science at best - certainly under 'field conditions'.
Years before I'd also been refused track access for a Yamaha R1 with the stock factory dustbin-sized exhaust can, which they insisted on noise testing at 3/4 max revs that day (@9,000rpm). The noise off the cam-gear was as horrific as you'd imaging and the bloke said that the 102dB it measured was too high and I was not allowed on. EU Type Approval plate on headstock read 78dB exhaust noise at 7,500rpm as homologation, which is almost silent. I complained and was asked to try a ride by reading instead, fortunately. Did a couple of laps and I think Parkie actually missed me first time round as he never heard me coming. It was quiet, of course, and I was allowed on.
It's all a conspiracy you know....
/RANT=OFF.
