How loud is 100db

[rje]

I am going to do my first track day (Keevil Airfiled charity day on 12th May) but it has 100db limit. I have no idea how loud my car is - a 1999 1600 road sport. I have an additional back box that I bought with the car that I could fir but would rather not unless I need to. Anyone got any advice? As far as I know the sit exghaust is the standard one.

Any thoughts most welcome.

Thanks

R

P.s. I would psot on Blatchat but my log in won't let me in!

[Sam_68]

100dB is pretty loud, but if you're concerned, try to visit a track day before the one you have booked and ask them to test it for you.

Alternatively, BookaTrack will hire you a noise meter for £9.00 or you can buy one from Maplins for about £30.

Edited by Sam_68 on Tuesday 8th April 23:12

[Tango7]

Hi,

The loudness of your car will depend on many factors. However, if its a 1600 K series car on a plenum and single throttlebody and a decent condition 5" or 6" exhaust (even better if it has the single pipe through the sideskin and the 4-1 manifold in the engine bay!), I think it will be a very safe bet to say it will be comfortably under the 100db limit.

TC's Superlight R with its throttlebodies and foam filter, external 4-1 exhaust and 6" silencer registers between 98-100db's and is definitely what you would think of as loud!

Sam's point about getting along to a trackday just to have it checked is a very good idea.

T

[ewenm]

If the Keevil day is with Motorsports Events, try to get along to one of their earlier days and they'll test your car for you. FWIW my 7 is 96dB and the Mustang is 106dB but VERY loud!

[Fat Arnie]

100dB is pretty quiet for a Caterham. Anything with throttle bodies or carbs and a 4:1 exhaust is unlikely to get below this figure.

[Noger]

Yes, it isn't that loud in the scheme of things.

Bookatrack will post you a sound meter for a few quid.

[Piers917]

My standard 1.6 Superlight on a 4-1 non-cat exhaust was 95dB at 4.5k revs static. I'd be surprised if your Roadsport was any louder than that.

Edited by Piers917 on Wednesday 9th April 10:12

[Tango7]

Also don't forget that when you are asked to rev your car to 3/4 revs, bring the revs up fairly gently and don't just blip the throttle as this will generate a spike on the noise meter which may take you over the limit

[Sam_68]

Piers917 said:

My standard 1.6 Superlight on a 4-1 non-cat exhaust was 95dB at 4.5k revs static. I'd be surprised if your Roadsport was any louder than that.

... and remember that the Decibel scale is logarithmic. IIRC ('tis a long time since I was at university!), an increase of 6dB is equivalent to a doubling of the sound level, so 100 dB would be not so far off twice the noise being generated by Piers917's car.

For what it's worth, my Westfield (1800 K-series on throttle bodies, no cat, and measured at 5,500rpm - as Tango says, measurements are taken at 75% revs, so the other way to improve compliance is to adjust your rev limiter to a lower figure ) measures at 94dB, but that's with a recently repacked silencer.

Silencer efficiency drops off with age (mainly because the sound absorbing fibreglass packing breaks down and blows out), so ultimately the only way to be sure would be to test it, but I'd be quite surprised if a car of your specification was over 100dB.

[Noger]

And also that static noise tests are not what get Caterhams thrown off track days. You might have a quiet exhaust, but the induction noise on the drive by meters (if they have one ?) is the killer. Bedford is a classic example.

[2 sMoKiN bArReLs]

did you know, 110 decibels is twice as loud as 100?

[Tango7]

I thought that an increase of 3db's was a doubling of noise so 100 to 110 is effectively 3x as much

[Sam_68]

Wikipedia reckons a 3dB increase represents a doubling of the sound energy, too.

But my vague recollection is that the human ear doesn't have a linear response and in any case the percieved noise level is very much dependent upon frequency. But as I said, it's a long time since I was taught it in Architectural Science at uni!

Whatever... the thing to remember is that even quite a big change in attenuation of sound energy from your exhaust system will only result in a small change in the dB reading.

[_TC]

rje said:

I am going to do my first track day (Keevil Airfiled charity day on 12th May) but it has 100db limit. I have no idea how loud my car is - a 1999 1600 road sport. I have an additional back box that I bought with the car that I could fir but would rather not unless I need to. Anyone got any advice? As far as I know the sit exghaust is the standard one.

Any thoughts most welcome.

Thanks

R

P.s. I would psot on Blatchat but my log in won't let me in!

RJE if you are around on satruday i am at Goodwood with bookatrack and if you popped by im sure they would sound test your vehicle for you. i am going from Basingstoke so not too far from you.

[rje]

Thanks guys.

The car has a standard side exit exhaust but also came wiht an extra back box and rear exit pipe. Decided to fit that yesterday just in case -nightmare getting it to go on but got it fitted in the end. Strange thing is it did not seem to make any difference to the noise of the car....

Think I have done all I can for now, so will go along as see, being gentle when reving the engine when it is being tested.

Thanks for all of hte help.

R

[RobM77]

Naturally get it checked to be sure. However, I'm checked at every circuit I go to in my 1.6 Roadsport race car (standard engine and exhaust) and have never been as loud as 100Db. A friend with a noise meter thingy tested me in all sorts of different scenarios and we couldn't get above about 95 if I remember rightly.

Edited by RobM77 on Wednesday 16th April 09:19