Noise Emissions
- Thread starter salisbees
- Start date
With a standard exhaust I am sure you will be fine. The test will be at 75% of maximum revs, not 4.5k. Noise test results are very variable however and my current car has been recorded by Goodwood at 97db one day and 100db on another; Rockingham test was 93db - go figure. Best to ensure you don't go over the target revs as they record the highest db.
As Ralph says a standard exhaust should be fine and as for the differences he has had on measurements any instrumentation depends for it's accuracy on it's calibration, then there is the fact that humidity has an effect on the passage of sound through the atmosphere and the difference in this humidity may be imperceptible to us but if measured correctly and atmospheric effects are catered for then you should not have a problem. I don't have data to demonstrate this but no doubt if anyone is really interested then it should be available on the internet.
Buddy, thanks for the help. For what it is worth there is no real help on the internet, only confusion, nor from the tracks as such information is only relevant to the day for the reasons stated. After pushing an OPC they finally got a statement from Porsche GB to the effect that at 3750 revs they would expect 98db which makes attendance on a 98db day in the lap of the testers [
]. I believe that the 987 does not have an issue as my 987 Boxster S had no problems. I need to do some more investigations both with 981s at tracks whilst testing is in progress and with exhaust specialists, as I am reluctant to purchase a 981 if I can't use it on 98db days.
]. I believe that the 987 does not have an issue as my 987 Boxster S had no problems. I need to do some more investigations both with 981s at tracks whilst testing is in progress and with exhaust specialists, as I am reluctant to purchase a 981 if I can't use it on 98db days.
Howard, You might want to speak with either Steve Kevlin or Paul Grainger (on +44 1608 652911) who run the Club's trackdays. They will be able to give you their experiences with noise tests on a range of circuits. Another data source could be to buy a sound level meter such as http://www.amazon.co.uk/dp/B0015NSTLI/ref=pe_385721_37986871_TE_item The test parameters are: • Measurements will be made at 0.5m from the end of the exhaust pipe with the microphone at an angle of 45° with the exhaust outlet and at a height of 0.5 to 1.0m above the ground • Where more than one exhaust outlet is present, the test will be repeated for each exhaust and the highest reading will be used. In circumstances where the exhaust outlet is not immediately accessible, the test may be conducted at 2.0m from the centre line of the vehicle at 90° to the centre line of the vehicle, with the microphone 1.2m above the ground (Cayman has only one/S has two close together = one) • Measurements should be made outdoors with no large reflecting objects (e.g. walls etc.) within 3.0m (in the 0.5m test) or within 10.0m (in the 2.0m test) I really don't see that you will have problems (BTW Porsche db is not correct in my experience especially as the result was at just over 50% of revs), but understand your need for some certainty on a key decision.
Ralph, Thanks for that, I had no idea that a meter was so cheaply available [] I have discussed the issue with the track day team and other organisers and, of course, it is not an issue at PCGB days as they run at 105db and my 991 meets that level provided I do not use the sport plus or lift off by the microphones [8D] ......... Amazon here I come!
] I have discussed the issue with the track day team and other organisers and, of course, it is not an issue at PCGB days as they run at 105db and my 991 meets that level provided I do not use the sport plus or lift off by the microphones [8D] ......... Amazon here I come!
Howard, For noise test process, see https://www.goodwood.com/motorsport/track-day-experiences/noisemanagement/noisemanagement.aspx the video shows a static noise test, the track side drive by microphones and how noise is monitored during the event. Sorry if I am telling you stuff you know but the drive by limits are lower than the static (generally by 3db or more) and are additionally less onerous being measured further away from the car. At Thruxton for instance where there is a 90db static limit, they happily let my Carerra GTS through because it would not and did not trip the drive by even with sport exhaust on. I am not sure from your last post whether you are looking at a 991 (Carerra) or a 981 (Cayman) but Thruxton have a fleet of 981 non-S Caymans for circuit school tuition http://www.thruxtonracing.co.uk/experiences/porsche-cayman-thrill (they need to update their picture so all are 981s)
Ralph/Howard, As someone who was involved in sound and vibration measurement in the vehicle, aerospace and defence industries for more than 30 years, the sight of an official waving a a sound level meter around in the vicinity of an exhaust pipe fills me with dispair..! A sound level meter is a precision instrument which requires careful calibration and use in order to obtain an accurate sound pressure level [SPL] reading. Leaving aside the fact that the meter needs to be positioned correctly in order to get a consistent reading [distance and angle from exhaust and height above ground], as Kevan has pointed out, atmospheric corrections [pressure, temperature, humidity and wind speed] should also be applied in order to obtain an accurate SPL measurement. Bearing in mind that the decibel is a logarithmic unit where a 3dB change represents a doubling/halving of the SPL, even 1dB represents a significant sound level difference, so accuracy of measurement is essential. I have to say that, despite its limitations, trackside measurement of noise levels would seem to be a more representative method for assessing the environmental impact of track activity on the locality but I can't help thinking that it would be better also to take simultaneous measurements in that locality for correlation. Jeff
Guys, Thank you, all information gratefully received. FYI, I have a 991 C2S and am considering a 981 to allow me to attend 98db days as well as 105db days. Goodwood has allowed me to run on a 98db day providing I did not exceed the drive by limit (which I didn't) but would not confirm a repeat performance. Currently, I run a Toyota MR2 on 98db days but age is creeping up on it!
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