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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!
Gareth
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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.
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Joined: Jul 2018
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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. I've had a bit to do with noise testing commercial aircon, and you're right it always seems to be more of an art than a science, but 10db difference is huge, I wonder how often the circuits calibrate their measuring equipment?
Gareth
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Annually at minimum to comply with MSA from what I remember, as a former trainee Environmental Scrutineer. From the same role I'm also aware of how difficult it can be to get an accurate reading. However, from MSA perspective it is overall noise, not just exhaust. The instructions are to not carry out noise tests in a confined area. (It's a few years since I did any of this so rules may have altered and my memory is not quite what it was   )
Graham (G4FUJ)
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Another update from the importer:
Morgan refused to change the CoC
They are now working with an exhaust specialist to build a custom exhaust that will record 86dB in accordance with the Swiss measuring regulations.
Car due back 19th October
2010 Aero Supersport | 2017 VW Multivan | 1996 BMW M3 Evo
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I've had a bit to do with noise testing commercial aircon, and you're right it always seems to be more of an art than a science, but 10db difference is huge, I wonder how often the circuits calibrate their measuring equipment?
Richard
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Has a lot to Say!
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I love the "power gain factor" 
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Double of loudness perception is almost a factor of 6dB. http://www.sengpielaudio.com/calculator-levelchange.htmAh I see, Sengpiel uses the same sheet you have posted, Richard, further down on his page.
Last edited by Heinz; 07/10/18 12:15 PM.
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Meanwhile I got an email from "my" exhaust man who is scratching his head on how it would be possible to get the sidepipes down to 86dB.
It is now just a waiting game
2010 Aero Supersport | 2017 VW Multivan | 1996 BMW M3 Evo
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My exhaust man was right - not a chance in hell of hitting 86dB - but it is now down to 91dB - which is withing 3% or 5dB of the CoC limit.
Which means the car failed.
Failed? Yes - failed.
But it passed the noise test? Yes - but it failed to have any paperwork for the exhaust
So what this means is the car will tomorrow get booked in at FAKT to have the exhaust homologated - which is good news for me, but less good news for any other sidepipe equipped Supersport in Switzerland.
My understanding is that once the homologation has been completed and the paperwork submitted to the STVA only those cars equipped with this particular side exhaust will pass the MFK.
I will get all this clarified - and also provide details of the exhaust supplier - in due course, and once the car is sat back on my drive!
2010 Aero Supersport | 2017 VW Multivan | 1996 BMW M3 Evo
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