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Re: measuring noise levels - help needed

Subject: Re: measuring noise levels - help needed
From: "Mike Rooke" picnet2
Date: Sat Sep 29, 2012 8:50 am ((PDT))
    I contacted Vicki off list with some estimates based on the measured 
sensitivity of the capsules (since I supplied and measured them before 
shipping) - given some error in the measurements related to the boundary they 
are mounted on, plus temperature & distance effects. Using a fiddle factor I 
gave a couple of estimates for the SPL based on low sensitivity and gain 10 of 
the LS10. -Rough estimates at that.

Using phones as SPL meters works providing you have a decent calibrator and can 
calibrate the (external) capsule, ignoring the response differences compared to 
a flat mic, the iphone manages down to around 20dBA with the EM172. Or used to 
Ive not checked or used it in a while for SPL measurement.  Signal Scope pro 
for ios works well...


--- In  "mipartitus" <> wrote:
> Hi Vicki,
> Good sound level measurement is a science in itself, but just to get an idea 
> you can in principle use a recording like you made, as long as your recording 
> chain has somehow been calibrated. I did this for an Olympus LS-5 and EM-172 
> capsules (in free field, no boundary rig), for all recording levels. I wanted 
> to upload the resulting graph, but it seems there is no room left for new 
> files in our Files directory.
> So here are the raw numbers: to get the sound pressure in Pascal from the 
> recorded wave file (assuming numbers range from -1.0 to 1.0, which is 
> standard in most editing/analysis programs) one has to multiply the value in 
> the recording with: 27.22, 7.18, 3.57, 2.32, 1.68, 1.09, 0.80, 0.55, 0.43, 
> 0.41 for recording levels 1-10 MIC Sense LOW, and 3.22, 0.70, 0.36, 0.24, 
> 0.17, 0.13, 0.09, 0.06, 0.05, 0.05 for recording levels 1-10 MIC Sense HIGH.
> There may well be a difference between the LS-5 and LS-10, and of course the 
> boundary rig has an effect too, so there probably is little point in using 
> these multiplication factors for this specific recording. But if you have 
> loose EM-172's and an LS-5 you could give it a try (with the obvious benefit 
> that you can make unattended long-term recordings, and then later measure the 
> noisy parts).
> If the info above is not helpful in your case, in may be of interest to 
> people who use the LS-5/EM-172 combination, and who want to get an estimate 
> of, or reproduce, the absolute sound levels of the auditory scenes they 
> recorded.
> Best, Gabriel
> --- In  vickipowys <vickipowys@> wrote:
> >
> > All,
> > 
> > Its spring in Australia, the birds are singing, but school holidays  
> > have just started and kids on motor bikes are doing constant circuits  
> > on the property next door.  One new 2-stroke bike is particularly  
> > annoying.  There is a 1-minute recording of it on SoundCloud here:
> > 
> >
> > 
> > I would like to be able to get a rough estimate of its noise level  
> > for legal reasons.  Does anyone know how I can estimate a decibel  
> > reading from this recording?  Details of equipment are on SoundCloud.
> > 
> > My legal advice is that I have 'an entitlement to the quiet enjoyment  
> > of my property' and that the 2-stroke motorbike noise constitutes 'a  
> > legal nuisance'.
> > 
> > Being able to measure the actual noise level would be a bonus.
> > 
> > Thanks in advance,
> > 
> > Vicki Powys
> > Australia
> >

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