trackday noise limit advise

[richardm6994]

Hi everyone, this is my first post and I'm hoping there is someone on here that has the answer.....

Does anyone know what frequency tracks around the UK take the noise measurement at?

The company I work for has many £££'s worth of acoustic labs and measuring equipment. Today they took a measurement off my car (0.5m from exhausts @ 45degrees angle)......it's 106.2db @ 500hz or 99.5db @ 1000hz

Obviously this is critical to me because if tracks measure at 500hz...then I'm too loud for nearly all track days, but if they measure at 1000hz (which our technical director seems to think would make sense) then I'm ok for most trackdays.

I'm no expert, but I do know that measuring sound isn't as simple as measuring other things .........you can get different results depending on how the db-meter is set up.

Firstly there is 'sound-weighting'.....my measurements were taken at z-weight but if they were taken at a-weight then my 500hz would yeild a different result. I'm assuming that the tracks measure at either A-weight or Z-weight??

Then there is what sound frequency they take the measurement at....as can be seen from my results there is nearly 7db difference between 500hz and 1000hz......which makes all the difference when I'm as close as I am to the trackday limits.....

I would of thought given the sophistication of the motorsport world....there must be a standard frequency that they measure car noise at.....to me common sense would be 1000hz but through all the docs I've read ECE reg no. 51 etc.....I can't find any reference!!

Is there anyone out there who has the answer!!!!

[LFAwhoosh]

I doubt you'll get a good answer - some tracks don't even know their own noise rules - for example the paper bedford sound management plan approved by the council dictates that someone black flagged for noise gets another chance if they make an exhaust change, but the organisers almost always stipulate day over on a first noise meter trip.

Quite often it's driveby rather than static Db which causes more issues too. Some organisers offer a free static noise test on arrangement though, perhaps you should take advantage of this.

[QBee]

They measure dB(A) at 3/4 of your rev limit in the static test, as you said 0.5 meters, 45 degrees.
They measure dB(A) at 20 meters on drive by.

The Bedford noise limits are 101 static, 87.5 drive by. I struggle with the static, no issues with drive by.

HTH

[gruffalo]

I don't think they measure at a certain frequency but more like a white noise test of the total sound pressure at the back of the car, this is why many rear engine cars can have problems with a static test even though the exhaust itself is not that noisy.

Static testing is in my mind pointless.

[QBee]

gruffalo said:

I don't think they measure at a certain frequency but more like a white noise test of the total sound pressure at the back of the car, this is why many rear engine cars can have problems with a static test even though the exhaust itself is not that noisy.

Static testing is in my mind pointless.

That explains something I couldn't understand. Thanks Martin.

While I was desperately trying to get my Chimaera under 101 dB last time out at Bedford, and was kneeling on wet tarmac at 0700 attaching my track day cans, PetrolTed rolled up in his Porsche GT3, the Dyson purring under the rear bonnet.......and proceeded to clock 103 DB too. The sound guys looked appalled, and had to resort to testing it just behind to driver's door. I am not sure they ever got him under 101dB, but as a consequence they passed us both with warnings that if we failed the drive by noise meters (87.5 at 20 meters) we were on our bikes.

Remind me never to buy a rear engined TVR......come to think of it, it has been rear engined a few times on track days

[gruffalo]

Just goes to show................static noise testing is pointless.

Will we be seeing you at snetterton on the 22nd September Anthony?

[QBee]

gruffalo said:

Just goes to show................static noise testing is pointless.

Will we be seeing you at snetterton on the 22nd September Anthony?

I was hoping to be there, but suspect it will clash with my holiday. First one we have had for five years. Dates not set in tablets of stone, as we will be touring, but I will not be popular if I try to cut it short for a track day......

[1441]

Another groan re static tests, bike engines like all cars BECs are tested at 3/4 max rpm, same engine in a bike, same track, same guy testing 1/2 max rpm?

Like a few above occasionally I have problems with static tests, never once had a drive by issue even after removing mods used to get through a static test?

[AdiT]

Does anyone have any experience of how much difference is there between static and drive-by readings? I mean actual readings rather than the limits. I regularly test between 96-98db static with my R1 Fury. Next month I've got a weekend away where the limit is 95db drive-by. Today at Blyton I was under 90db on their drive-by (even trying to be loud) but it is on a slowish corner.

[QBee]

AdiT said:

Does anyone have any experience of how much difference is there between static and drive-by readings? I mean actual readings rather than the limits. I regularly test between 96-98db static with my R1 Fury. Next month I've got a weekend away where the limit is 95db drive-by. Today at Blyton I was under 90db on their drive-by (even trying to be loud) but it is on a slowish corner.

Using the limits as a reference.......I struggle to get under 101 dB(A) static at Bedford, but never have a problem with their drive by limit of 87.5 dB (A), which is measured at three different places on the track. 95 dB drive by would seem to me to equate to 108-110 static.

[juansolo]

richardm6994 said:

I would of thought given the sophistication of the motorsport world....there must be a standard frequency that they measure car noise at.....to me common sense would be 1000hz but through all the docs I've read ECE reg no. 51 etc.....I can't find any reference!!

Good luck with that. It's a total crap shoot and it's pot luck whether you'll be over or not from circuit to circuit.

[QBee]

juansolo said:

richardm6994 said:

I would of thought given the sophistication of the motorsport world....there must be a standard frequency that they measure car noise at.....to me common sense would be 1000hz but through all the docs I've read ECE reg no. 51 etc.....I can't find any reference!!

Good luck with that. It's a total crap shoot and it's pot luck whether you'll be over or not from circuit to circuit.

My car comes out anywhere between 99 and 108 dB(A) on MSV circuits, all supposedly using the same model of calibrated professional noise meter. Perhaps it depends on every other factor - the proximity to buildings, other cars being close, weather, humidity etc.? I always arrive with the car fully warmed up and rev to 4500 rpm.

As said above, Bedford was 105 without add-on track cans, 103 with.
Cadwell Park a few weeks later was 108.5 without cans, 100.8 with.
Work that one out!

[mad4amanda]

Noise meters used at circuits should be A weighted and as such are measuring at 1khz, certainly the MSV ones I have used are.