Noise Level Meter App

[JJC]

Has anyone used an app for a noise level meter? Just seen the Castle Coombe advert in TRAction and remember the 2 had some difficulty at Goodwood. Would like to test it myself! JJC

[ianc]

As it happens, a friend of mine sent me the following this week:

I downloaded a free app for my Ipad: a Decibel meter so that I can check the exhaust noise on my V-Rod for the MOT….94dB at start up, then a steady average 87dB at idle, achieved by the engine management system cycling the idle speed in a neat saw-tooth like an old truck…

 

Ian Cornish

[JJC]

As it happens, a friend of mine sent me the following this week:

I downloaded a free app for my Ipad: a Decibel meter so that I can check the exhaust noise on my V-Rod for the MOT.94dB at start up, then a steady average 87dB at idle, achieved by the engine management system cycling the idle speed in a neat saw-tooth like an old truck

 

Ian Cornish

Great, but which one!?!?!? JJC

[Alec Pringle]

Be warned here, the only noise meter that matters is the official one at the circuit.

 

A N Other MSA approved meter should be a reasonable comparison, but even so make sure you err on the side of caution.

 

Whatever app for whatever other device is not going to cut any ice with the Castle Combe noise tester, or Wiltshire Council, and given the significantly different responses between measuring devices it is not wise to rely on any device other than the approved version.

 

Testing is at 4500rpm for all cars except motorcycle engined cars which are tested at 3/4 of maximum rpm - that is the initial test 100dB @ 0.5m.

 

Bear in mind that passing this is only the starter for ten, allowing you onto the track - the circuit is continuously monitored and it isn't hard to find yourself pulled off after a very few laps. It's all too easy to pass the static test, but then fail the drive-by meter. A problem that in particular affects Rover V8s, and also 5-banger Audis, which knocks our quicker cars out !

 

Cheers

 

Alec

[Motorsport Mickey]

One of the reasons I had a split exhaust system with outlets at midway down either side of the car, every little helps.

 

Mick Richards

[ianc]

JJC: Message from my friend Paul:

The app is called "Decibel 10th" and it is a free download.Hope he gets on well with it. People have compared it with commercial meters and found that it is pretty accurate.

 

But bear in mind the advice from Alec and Mickey.

Ian Cornish

[KOB]

An app is at best going to be a rough(very) guide my companies acoustician just fell about laughing when I told him that there were apps that do what is £4500 meter does !!!

[Ashley James]

I'm in the audio business and have Bruel and Kjaer as well as Calibrated SPL meters that double up as Mike preamps and they read very differently to phone Apps. This is partly because phones roll off steeply below 200Hz to make speech as clear as possible.

 

If you want an good SPL meter, try Maplin, Farnell, RS or CPC. They're not expensive, but you do need to understand how the vehicles are measured and do it exactly the same way or your readings will be different.

[Alec Pringle]

A few years ago a pal decided to record the TR8 Drag Car on his rather expensive and sophisticated mobile . . . . not at 0.5 metres as per scrutineering measurement, more like 5 metres. We blipped the throttle, it can't have got much above 4.500rpm before the microphone in the costly device self destructed. Believe me, a mobile with a blown mike is of limited value, and not cheap to repair.

 

Mobile phones are not intended to be used for motor sport noise measurement.

 

If you wish to check the MSA measurement technique you'll find it here

 

http://www.msauk.org/uploadedfiles/msa_forms/bluebooks/12/142_149_Common_Regulations_for_Competitors_(Vehicles)_(J).pdf

 

Anything reliable requires a Class 2 meter, which start at something over £200 and go up from there. Yes you can buy a £30 meter, but don't expect more than an approximation at best, and don't be disappointed when it doesn't agree with the scrutineer's meter.

 

Cheers

 

Alec

[Peter Cobbold]

A few years ago a pal decided to record the TR8 Drag Car on his rather expensive and sophisticated mobile . . . . not at 0.5 metres as per scrutineering measurement, more like 5 metres. We blipped the throttle, it can't have got much above 4.500rpm before the microphone in the costly device self destructed. Believe me, a mobile with a blown mike is of limited value, and not cheap to repair.

 

Mobile phones are not intended to be used for motor sport noise measurement.

 

If you wish to check the MSA measurement technique you'll find it here

 

http://www.msauk.org/uploadedfiles/msa_forms/bluebooks/12/142_149_Common_Regulations_for_Competitors_(Vehicles)_(J).pdf

 

Anything reliable requires a Class 2 meter, which start at something over £200 and go up from there. Yes you can buy a £30 meter, but don't expect more than an approximation at best, and don't be disappointed when it doesn't agree with the scrutineer's meter.

 

Cheers

 

Alec

If TRR owned an MSA-type meter we could all get measured at IWE.

First to wrap the needle round the stop wins.

[JJC]

Thanks

JJC: Message from my friend Paul:

The app is called "Decibel 10th" and it is a free download.Hope he gets on well with it. People have compared it with commercial meters and found that it is pretty accurate.

 

But bear in mind the advice from Alec and Mickey.

Ian Cornish

Thanks Ian I'll try it. I do know a bit about acoustics. Before I took the 2 round Goodwood I borrowed a SPL meter from a scrutineer friend. Discovered it was way over. So I put a different silencer set on. I've lost track of what happened after that but suspect that our super quiet 4 now has the socially responsible silencer set. All I was after was a very rough check - the App will do. Not that it matters but all measuring instruments, even expensive ones, are only good at the moment of calibration. JJC