Testing for tonality in environmental noise

[Julian Nichols]

Hi TRockers, I have a bit of an odd problem that perhaps someone more knowledgeable than me may be able to help me with.

For various legal reasons, I'm trying to measure some industrial noise that is occurring over a 24 hour period, roughly 800m from my premises, in a rural location in the South West of WA.

What I am trying to establish at this point is whether this continuous droning noise exhibits 'tonal' qualities as defined by documents such as the NSW Industrial Noise policy (2000).

Here's an excerpt from that document :

Establishing tonality

----------------------------------

Level of one-third octave band
exceeds the level of the
adjacent bands on both sides
by:
—5 dB or more if the centre
frequency of the band
containing the tone is above
400 Hz
—8 dB or more if the centre
frequency of the band
containing the tone is 160 to
400 Hz inclusive
—15 dB or more if the centre
frequency of the band
containing the tone is below
160 Hz

---------------------

From listening to the source, I'm confident that any tonality that might exist would be >400hz, so my understanding is that in order to establish tonality, I could conceivably :

Do a field recording using a laptop and a studio microphone. Run the audio through a plugin with a frequency analyser (Fabfilter Pro-Q or Schope by Scwha are two that I have, probably not the best for the job though), then look for any spikes. If I was to zoom in on an octave, and the spike in one third of an octave exceeded the other 2/3rds on either side by 5db, I would have established that the noise displays tonality as per that definition.

Am I on the right track? If there is a better way for me to do this (or better plugins etc to use), I'd gladly welcome any suggestions. It is just a preliminary test at this stage to determine whether or not it is worth paying for a proper environmental noise test to be conducted, with calibrated equipment. I realise that my testing is not going to stand up in a court of law, etc.

I'd be very glad to hear from anyone who might have some experience in this department, my knowledge of the technicalities of sounds and frequencies is a bit limited in this area.

[gigpiglet]

there is a good app called audiotools that along with a decent mic should be able to show you all this info... i use it for all kinds of on site sound measurement

[Kurt]

Most importantly, was the the noise already being made, or would a reasonable person expect that noise would be made, before you moved in?

[Julian Nichols]

My great grandmother gave birth to my grandfather in this house, so in the scheme of things this noise is a relatively recent thing

Gigpiglet, thank you very much for the recommendation, you were one of the people who I was keen to hear from, I suspected that you may have been able to help me. I'll definitely check that out.

The noise is affecting more people than me, so it's a bit of a community issue. I can't really say more due to the circumstances (and our old friend google linking this all to my real name), but anyhow... thanks!

[Kurt]

Audiotools is an iPhone app with an FFT spectrum analyser in it. The method you suggested would definitely do the same thing if you don't have the app and an iPhone compatible mic.

My great grandmother gave birth to my grandfather in this house, so in the scheme of things this noise is a relatively recent thing

Gigpiglet, thank you very much for the recommendation, you were one of the people who I was keen to hear from, I suspected that you may have been able to help me. I'll definitely check that out.

The noise is affecting more people than me, so it's a bit of a community issue. I can't really say more due to the circumstances (and our old friend google linking this all to my real name), but anyhow... thanks!

[TimC]

Hey guys,
Audiotools with a FFT is good but you need to spend the best part of $50 to get the app happening.. and then buy a mic for it.. and then leave your iphone on all night.
Recording the signal with a mic and watching it with a plug in FFT, like you suggested (Blue Cat Audio have a great free FFT too) - would be the easiest cheapest way to see where it's happening in the spectrum. You could get a time of occurence on your DAW too - Then you could look at getting an acoustic measurement guy in to do it "court-proof"