stevefoster Posted October 31, 2003 Share Posted October 31, 2003 Is there a rough rule of thumb to convert static 0.5m 45 deg angle dB test to approx drive by value. Any practical insight would be much appreciated. ? Static dB = 98 dba drive by or 100 db static = ? dba drive by In my case 104 dB static = ? dba drive by My racing info site here Hants (North) and Berkshire Area club site here Light blocks here Link to comment Share on other sites More sharing options...
Sheds Moderator Posted October 31, 2003 Share Posted October 31, 2003 Noise will obey the inverse square law, like all energetic radiation. This means that if you double the distance you divide the noise by 4. Consequently small changes in distance to the meter will have a big effect. Link to comment Share on other sites More sharing options...
Jason Plato Posted October 31, 2003 Share Posted October 31, 2003 I dont think its possible to link the two together , using my car as an example . I record 98Db static ( 0.5m @ 4500rpm ) , most of this noise comes from the exhaust tailpipe . The drive by noise is dependant upon the position of the noise meter relative to your car , engine speed , engine load and most of all what type of induction you are using - inside bonnet or poking out . Position of the meter can vary from day to day or track to track . As a practical example at Donnington , I run a K with throttle bodies, the trumpets are poking out of the bonnet enclosed within a Ram air filter . I recorded the normal 98Db static for my car , nowever the drive by noise is measured by a microphone below the gantry on the start / finish line .This for me is about 7500rpm under full load in 4th gear ( about as noisey as it gets ) the recorded level was 107Db On the same day a superlight R also recorded 98Db static , but then recorded 103 Db drive by .The induction on the SLR was the normal filter enclosed behind the bonnet . The limit for the day was 105Db drive by ( except when a 747 flies over ) the nice official asked me to short shift to 5th gear , I then recorded 105Db 😬. Hope this helps . dave Edited by - Dave Jackson on 31 Oct 2003 07:59:32 Link to comment Share on other sites More sharing options...
AMMO Posted October 31, 2003 Share Posted October 31, 2003 Steve Most people I have spoken who have had noise problems say that their drive-by is higher than their static. I hear stories of lifting off or short-shifting in the vicinity of the noise meter. As the others have said it is dependant on a lot of factors. If you are 104 dB static, don't expect to be quieter when you are flat on the gas. AMMO Link to comment Share on other sites More sharing options...
philwaters Posted October 31, 2003 Share Posted October 31, 2003 Why don't you stick the extra rear silencer back on for Donington? Will it fit with the slicks? Phil Waters - Having trouble sleeping? Click here You mean you can drive these? I thought it was just there to polish 😬 Link to comment Share on other sites More sharing options...
stevefoster Posted October 31, 2003 Author Share Posted October 31, 2003 98dba drive by strikes me as being tough for my 7. Even with the extra whisper box on the back the induction is the same. The extra box does not seem to restrict performance any, 2.5" straight through. Hants (North) and Berkshire Area club site here Light blocks here Link to comment Share on other sites More sharing options...
Jason Plato Posted October 31, 2003 Share Posted October 31, 2003 Steve , why do you need 98Db ? I thought Bedford areodrome was the only place that had this ultra low limit ?? I dont think you or me will ever get less than 105 db drive by with your carbs or bodies poking out the bonnet . Unless you cheat of course and lift the throttle , but then many circuits have multiple microphones ....... Dave Link to comment Share on other sites More sharing options...
stevefoster Posted October 31, 2003 Author Share Posted October 31, 2003 Donnington Saturday track day. I'll stick to racing... Hants (North) and Berkshire Area club site here Light blocks here Edited by - stevefoster on 31 Oct 2003 11:31:20 Link to comment Share on other sites More sharing options...
Rob Walker Posted October 31, 2003 Share Posted October 31, 2003 Goodwood ???? Link to comment Share on other sites More sharing options...
Strangely Posted November 1, 2003 Share Posted November 1, 2003 Steve, I got through fine. They mentioned in the briefing that they had to be strict on noise, but I don't think anyone got black flagged. There was a very noisy Vauxhall Seven there, and several other cars were quite loud. Not sure, but I think they may have unofficially relaxed the rules because there were so few cars there. Link to comment Share on other sites More sharing options...
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