Noise testing at home?
Discussion
I realise this has probably been done to death before, so I apologise, but is there a reliable way to noise test a car at home? I've just stopped single seater racing after ten years and now have a tin top racer which I can take to track days, however these are usually quite strict on noise compared to test days. I've tried three iPhone apps claiming to test noise and they all read differently by quite a large margin (enough to make them useless). Any tips? Getting the car to a track is a pain because it's not road registered, so I'd have to trailer it there.
I've found noise testing to be random enough at tracks, never mind at home.
I've tried iphone apps which seemed in the right ball park, and were useful for testing reduction in noise when fitting decibel devils and the like.
I later upgraded to a proper (but cheap) noise meter, and the results still didn't fully match the circuit results.
Having said that, the results at Snetterton didn't correlate with Brands Hatch either. (Which meant I spent a load of money on silencers to get on a Brands GP day, and then actually passed the test with nothing fitted)
I've tried iphone apps which seemed in the right ball park, and were useful for testing reduction in noise when fitting decibel devils and the like.
I later upgraded to a proper (but cheap) noise meter, and the results still didn't fully match the circuit results.
Having said that, the results at Snetterton didn't correlate with Brands Hatch either. (Which meant I spent a load of money on silencers to get on a Brands GP day, and then actually passed the test with nothing fitted)
I bought one of those cheap ebay 10 quid meters for getting my car through IVA. It was within 1db of VOSA's meter and hasn't lead me astray with the track ones. The phone apps don't work so well as the microphones aren't really built for the job. Easy peasy to do if you have a willing assistant.
I have the Niosh Sound Level meter , asked the wife to keep the throttle at a
steady 3/4 revs (big mistake) and it was all over the place and my legs nearly
set on fire when she revved it to 8000 rpm plus !
Took it to Brands Hatch 104.2 decibels took the same car to Snetteton
same revs , 106.2 .
So even MSV results are not the same .
Ended up making my own baffled inserts which reduce the sound by about
4-5 decibels.
steady 3/4 revs (big mistake) and it was all over the place and my legs nearly
set on fire when she revved it to 8000 rpm plus !
Took it to Brands Hatch 104.2 decibels took the same car to Snetteton
same revs , 106.2 .
So even MSV results are not the same .
Ended up making my own baffled inserts which reduce the sound by about
4-5 decibels.
I have the Niosh Sound Level meter , asked the wife to keep the throttle at a
steady 3/4 revs (big mistake) and it was all over the place and my legs nearly
set on fire when she revved it to 8000 rpm plus !
Took it to Brands Hatch 104.2 decibels took the same car to Snetteton
same revs , 106.2 .
So even MSV results are not the same .
Ended up making my own baffled inserts which reduce the sound by about
4-5 decibels.
steady 3/4 revs (big mistake) and it was all over the place and my legs nearly
set on fire when she revved it to 8000 rpm plus !
Took it to Brands Hatch 104.2 decibels took the same car to Snetteton
same revs , 106.2 .
So even MSV results are not the same .
Ended up making my own baffled inserts which reduce the sound by about
4-5 decibels.
Far Cough said:
Problem is you'll get booted off for the drive by test not the static test and I have not found a way of testing that without upsetting the neighbours !!
It's a noisy day that I know I'll breeze through, but they'll test me to see if I can go along to their cheaper quiet days.Sound can be effected by so many things and this often leads to the confusion. What kind of surface you're on, wind, angle, distance etc. A heavily cammed engine will be noisier than a soft cam.
I remember breaking the driveby at Donny by quite a lot with a two silencer turbo car, we had an old empty paint tin in the back of the tow van so cut it open and fitted a slice of it like a flap over the end of the tailpipe with a hose clip so it directed the gasses down. It passed no problem.
I remember breaking the driveby at Donny by quite a lot with a two silencer turbo car, we had an old empty paint tin in the back of the tow van so cut it open and fitted a slice of it like a flap over the end of the tailpipe with a hose clip so it directed the gasses down. It passed no problem.
RobM77 said:
Great news. My car was measured yesterday by Castle Combe at 98Db. That means I can do track days 
I was at Castle Coombe on Friday and really struggled with the noise testing - varying results on two different tests from 105 - 102 !! Last time I was there, the car read 98. They (and I) couldn’t understand it - And I agree there is an annoying discrepancy between readings at all tracks. In fairness to Castle Coombe they let me go out with a ‘Decibel Slayer’ on (but I wouldn’t recommend them - car drove horribly and back pressure created a lot of fumes in the car). They then let me try without it, to see if I set off the noise alarms. I was fine and ultimately no problem. They are very helpful at Castle Coombe but not sure all tracks are as friendly.
I find most tracks are as friendly as they can be - they have to tread the fine line between us, who they want to get on track, and the local councils, who want to close them down because local residents are constantly complaining about the noise, even though in most cases the tracks have been there considerably longer than most of the residents.
If you suspect your car will be close to the limit, having one, a pair of, or even four (these days, with manufacturers' obsession that anything "sporty" must have more tail pipes than the QE2) bolt on cans, with you at least shows you are trying to comply. Also bolt on cans do have the effect of taking the harsh edge off the tone of the exhaust note.
Also, lets be honest here, anything over say 95 decibels could hardly be classed as "quiet" in the first place.
My alternative solution was quite unintentional - I stuck a big turbo on my TVR, and it knocked 10 decibels off the noise level overnight.
If you suspect your car will be close to the limit, having one, a pair of, or even four (these days, with manufacturers' obsession that anything "sporty" must have more tail pipes than the QE2) bolt on cans, with you at least shows you are trying to comply. Also bolt on cans do have the effect of taking the harsh edge off the tone of the exhaust note.
Also, lets be honest here, anything over say 95 decibels could hardly be classed as "quiet" in the first place.
My alternative solution was quite unintentional - I stuck a big turbo on my TVR, and it knocked 10 decibels off the noise level overnight.
peekay74 said:
I was at Castle Coombe on Friday and really struggled with the noise testing - varying results on two different tests from 105 - 102 !! Last time I was there, the car read 98. They (and I) couldn’t understand it - And I agree there is an annoying discrepancy between readings at all tracks.
In fairness to Castle Coombe they let me go out with a ‘Decibel Slayer’ on (but I wouldn’t recommend them - car drove horribly and back pressure created a lot of fumes in the car). They then let me try without it, to see if I set off the noise alarms. I was fine and ultimately no problem. They are very helpful at Castle Coombe but not sure all tracks are as friendly.
Hmm, yes. On race day I measured 102Db! Considering it's a logarithmic scale, that's quite a difference.In fairness to Castle Coombe they let me go out with a ‘Decibel Slayer’ on (but I wouldn’t recommend them - car drove horribly and back pressure created a lot of fumes in the car). They then let me try without it, to see if I set off the noise alarms. I was fine and ultimately no problem. They are very helpful at Castle Coombe but not sure all tracks are as friendly.
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