How loud is 105db..

[chris_c201]

....appreciate there is potential for some smart a.. comments based on my question but...

For track days at Kames, it says the noise limit is 105db and I've no idea in practical terms how loud that is and whether my Evora with decat and intake will be okay?

I'm guessing the apps you can download for your phone are unlikely to be remotely accurate?

Any advice appreciated!
Chris

[Dominic]

Having heard your (very sweet sounding) car, I'd reckon it would be under 105db. I have heard louder - that have passed noise tests. Also heard louder at Kames.

I would think the difficulty of performing a noise test using a phone, or any other piece of equipment, would be getting the angle, distance and revs all totally correct. A little out of position could give a significant reading... IMHO.

Await to be proven wrong now!

[Scottish Scrutineer]

Hi Chris,
105dB is pretty loud. For MSA sprint events, the measurement is made at 2/3 max revs and measured at 45degrees and 0.5m from the exhaust, and the limit is 108dB. You need to check what the revs and distance are for the Kames Club events.

To be honest the iPhone apps are not too far off on accuracy, but you do need to have free space about the car so there are no reflected noise paths. Other considerations are to make sure the engine speed is nice and steady at the point of measurement, and everything is fully warned up. With some cars, disengaging the clutch, making sure the transmission noise doesn't add can help. Induction noise can also be a pest, so if marginal, stick a paper filter in rather than a high flow fabric one.

Where about are you? Perhaps I can point you in the direction of a colleague with a noise meter. I'm in Dalgety Bay if that's any use.


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Renny

[GBOBM]

Chris if this is for the event on the 19th of Jan, then you are definitely too loud.

[Dominic]

Chris if this is for the event on the 19th of Jan, then you are definitely too loud.

Yes, and so are you, and Lewis!

[chris_c201]

Hi Chris...

Renny

Renny - thanks very much for the info, much appreciated, I'll maybe try the app method to get a ball park and if it's close try and get something more accurate.

As for the 19th, I'm too rubbish to worry about

[Al.]

105 as mentioned is really quite loud. Working offshore we have all sorts of noise restrictions and measurement of zones for hearing protection and VERY few even get over 100. I have checked all 3 Apps I have on i-Phone against a calibrated sound meter on board and have to say was very surprised at how accurate they were (& all 3 seem to agree with each other which may be a limitation of the phone mic). It will definitely give you a good indication. The other thing would be is it a static test like at a MSA event as noted by Renny or a "drive by" test where you are likely to get away with a lot more and can even lift off for that bit if a known location. Maybe against the spirit of the idea I appreciate before I'm shot down, but if you were borderline may help.

My previous 2010 Evora was decatted and with Sports Exhaust and wasn't over 105Db on a drive by I did with my neighbour and our phones. Something in the high 90's. Remembering every increase in 1 Db is an increase in noise of 2 or something as on an exponential scale or something. (I should know but can't be bothered going to look) However the newer S with 2013 Exhaust and adjustment valve on the S button is much louder.

[GBOBM]

Chris, I don't think you're anywhere near 105db

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[Andy G]

Would be amazed if you hit 100db.

If you car is 105db, you want to think about ear protection for prolonged use or you will be deaf as a post.

[Scottish Scrutineer]

3dB increase is a doubling of sound energy. Also important is distance, as you double the distance from a single source, you reduce by 3dB (given perfect free sound field)


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Renny

[philthy]

Your evora will be fine, you would probably need pipes straight from the manifold to reach 105db.

Now that I would like to hear!

[robin]

What scale (units/reference level) do the motorsport static sound test meters use? Is it dB (SPL)?

Cheers,
Robin

[Scottish Scrutineer]

This table shows the MSA noise measurement in dB(A) Robin.


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Renny

[robin]

Interesting that they use A-weighting. A weighting is probably inappropriate for the noise they are trying to measure! However, I guess it is used because the equipment is generally available.

Anyway, dB(A) is just dB(SPL) with some offsets subtracted at low and high end of the spectrum to account for the human perception of loudness.

This means it's a field (amplitude) quantity, not a power (energy) quantity.

As a result dB(SPL) is computed as 20 x log(A1/A0) where A1 is the measured amplitude and A0 is the reference amplitude (in this case 20 microPascal).

If you double the amplitude you go up by 6dB on the scale.

Similarly if you double the distance from noise source to sound meter you go down by 6dB on the scale (assuming no reflections, etc.).

If you are measuring sound intensity (power) then those 6's become 3's, but you aren't (at least I don't think you should be based on your handbook extract).

At least that's my understanding of it (which could easily be wrong).

Cheers,
Robin

[flyingscot68]

What intake have you got Chris, did you go for the Radium?
I've got that plus decat and sport exhaust and it's no where near 105db. I watched my wife go by the pit lane at Oulton a few times and my car was one of the quieter ones on track, you shouldn't have any problems.