DannyBoy Posted August 25, 2011 Share Posted August 25, 2011 I'm seriously considering going for one of the AAM 2.5 inch True Dual exhausts with a set of their high flow cats as well, but as I really would like to track the car once i get it tuned and therefore need to meet the 98db noise limit. Z1 say that the 2.5 inch is pretty tame 'for a true dual', but i have A) never heard a true dual in the flesh so for all i know a tame true dual could still be stupidly loud and don't know how loud 98db is in the real world so i don't know what i'm up against. So basically, i was wondering if anyone who's been to a track day and has an idea of how loud you can get away with and suggest whether i could get away with a reasonably loud exhaust or whether i should forget the whole AAM thing and go for a Milltek and Berks instead. Thanks DB Quote Link to comment Share on other sites More sharing options...
Vik54 Posted August 25, 2011 Share Posted August 25, 2011 Really depends on how close the track is to residential area as to how strict they are with imposing their DCb limit - it will be easy to surpass 98 with a TD and high flow cats but unlikely a track would turn you away Quote Link to comment Share on other sites More sharing options...
Sam Mcgoo Posted August 25, 2011 Share Posted August 25, 2011 My 2.5" True Dual Invidia with mid-pipe resonators and decats measured 97db @ 5k rpm. That's with a supercharger (which makes it louder) I would say mine is a quiet exhaust though, although it does really roar when at WOT. I think the tone makes a big difference though cause it doesn't drone whatsoever. Quote Link to comment Share on other sites More sharing options...
DannyBoy Posted August 25, 2011 Author Share Posted August 25, 2011 Thanks for the responses guys, @ Sam Mcgoo, if your supercharged Zwith true dual and decats came in at 97, i would hope that my NA z with this true dual and HFCs rather than decats would come in 98 or under. Worst case scenario i'll have to stick to bedford autodrome with their 102db limit. DB Quote Link to comment Share on other sites More sharing options...
stubzie83 Posted August 25, 2011 Share Posted August 25, 2011 As a sound engineer I can tell you that 98dB is quite loud. Depends whether is 98dB unweighted or 98dBA which is 'A' weighted and gives a more accurate reading of what the perceived loudness is to the human ear. 98dBA will be a lot louder than 98dB unweighted. For example the sound of a pneumatic drill at 1 metre is about 95dBA. For reference anything over 85dBA is considered to be damaging to human hearing and current health and safety legislation dictates that you shouldn't be exposed to these levels for more than 8 hours per day without hearing protection. At 97dBA the max permissible exposure time is 30 minutes before permanent damage occurs and at 115dB it's 30 seconds! For every 6dB increase the sound pressure (amplitude) doubles and the human ear perceives a doubling of amplitude for an increase of about 8-10dB. So if for example the stock exhaust is 80dBA then at 98dBA then the amplitude will be about 8 times that of the stock exhaust and will sound about 4-5 times louder. Quote Link to comment Share on other sites More sharing options...
DannyBoy Posted August 25, 2011 Author Share Posted August 25, 2011 As a sound engineer I can tell you that 98dB is quite loud. Depends whether is 98dB unweighted or 98dBA which is 'A' weighted and gives a more accurate reading of what the perceived loudness is to the human ear. 98dBA will be a lot louder than 98dB unweighted. For example the sound of a pneumatic drill at 1 metre is about 95dBA. For reference anything over 85dBA is considered to be damaging to human hearing and current health and safety legislation dictates that you shouldn't be exposed to these levels for more than 8 hours per day without hearing protection. At 97dBA the max permissible exposure time is 30 minutes before permanent damage occurs and at 115dB it's 30 seconds! For every 6dB increase the sound pressure (amplitude) doubles and the human ear perceives a doubling of amplitude for an increase of about 8-10dB. So if for example the stock exhaust is 80dBA then at 98dBA then the amplitude will be about 8 times that of the stock exhaust and will sound about 4-5 times louder. Awesome info, yea they measure dB(A) half a metre from the exhaust tips, I would hope the new exhaust would be just a little quieter than a pneumatic drill DB Quote Link to comment Share on other sites More sharing options...
evilscorp Posted August 25, 2011 Share Posted August 25, 2011 I have a true dual and its too quiet so I bought some de-cats will have them fitted on the 9th sept so dont think you will have much problems mine is 2.5inch too. Quote Link to comment Share on other sites More sharing options...
stubzie83 Posted August 25, 2011 Share Posted August 25, 2011 As a sound engineer I can tell you that 98dB is quite loud. Depends whether is 98dB unweighted or 98dBA which is 'A' weighted and gives a more accurate reading of what the perceived loudness is to the human ear. 98dBA will be a lot louder than 98dB unweighted. For example the sound of a pneumatic drill at 1 metre is about 95dBA. For reference anything over 85dBA is considered to be damaging to human hearing and current health and safety legislation dictates that you shouldn't be exposed to these levels for more than 8 hours per day without hearing protection. At 97dBA the max permissible exposure time is 30 minutes before permanent damage occurs and at 115dB it's 30 seconds! For every 6dB increase the sound pressure (amplitude) doubles and the human ear perceives a doubling of amplitude for an increase of about 8-10dB. So if for example the stock exhaust is 80dBA then at 98dBA then the amplitude will be about 8 times that of the stock exhaust and will sound about 4-5 times louder. Awesome info, yea they measure dB(A) half a metre from the exhaust tips, I would hope the new exhaust would be just a little quieter than a pneumatic drill DB Yeah the perceived loudness will be based on the tone of the sound as well. Most exhausts have quite a narrow frequency range and less high frequencies so don't necessarily sound as loud as say a drill which has lots of frequency content and is an unpleasant sound. Of course it will be a lot quieter inside the car as you won't have your ears half a metre from the pipes. Also sound levels in open air tend to halve (-6dB) about every 7 metres which is why at outdoor gigs they have to have speakers placed at varying distances from the stage to keep the sound level up for those people who couldn't make it to the mosh pit at the front Decats are quite loud, I was behind an Impreza STi with decats yesterday and it drowned out the sound of my zeds exhaust and the radio (on 30mph roads) and smelt quite bad. Quote Link to comment Share on other sites More sharing options...
garetgax Posted August 25, 2011 Share Posted August 25, 2011 [ it will be easy to surpass 98 with a TD and high flow cats but unlikely a track would turn you away ]............sorry to totally disagree but yes they would. Donny are ultra strict and have sensors all round the track. Bedford is very strict as well. Others arent as bad but all of them are becoming more and more strict in enforcement. Look at baffles if its too loud but bear in mind a pop charger will add to the noise as does the engine itself and also if the car is FI then turbo noise as well. My impreza got thrown off at donny once for noise but I just went on noisy days then (more expensive though). Quote Link to comment Share on other sites More sharing options...
djtimo Posted August 25, 2011 Share Posted August 25, 2011 Guys 98dB Is not too bad, My exhaust is about 112dB at 4750rpm! It hits a bit of a strange tone around there and the noise output jumps up! lol.. Check out these video's of my car for some idea of dB. The first is my 5ZIgen which was tested at 93-94dB at most tracks I have been on. (much nicer sound than my current set up ) The next is 3.5" down pipes (big bore de-cats) with the 5Zigen rear cans on a custom 2.5" true dual. cold idle. 4.75K RPM Track test rev's Its about 95-96dB at 4K tested at TOTB last month, I still need some extra silencers as it fails most strict track day noise limits! Quote Link to comment Share on other sites More sharing options...
Keviswatt Posted August 25, 2011 Share Posted August 25, 2011 To give you an idea, and I'm not sure it will help but 98db is the legal limit that recorded or live music in pubs are allowed to be played at K Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.