Comparing acoustic data (units question)
Comparing acoustic data (units question)
(OP)
I wanted to compare noise levels for a couple different data sets I have seen presented in papers. Each one of the papers seems to plot their noise level spectrum levels using different units:
dB re 1 microPa^2/Hz @ 1m
dB re 1 microPa/sqrt(Hz) @ 1m
dB re 1 microPa/sqrt(Hz) RMS @ 1m
dB re 1 microPa/Hz
How do I convert values presented in PSD (microPa^2/Hz) or spectrum level (microPa/Hz) into source level units (microPa/sqrt(Hz)) so I can make an 'apples to apples comparison?
Thanks
dB re 1 microPa^2/Hz @ 1m
dB re 1 microPa/sqrt(Hz) @ 1m
dB re 1 microPa/sqrt(Hz) RMS @ 1m
dB re 1 microPa/Hz
How do I convert values presented in PSD (microPa^2/Hz) or spectrum level (microPa/Hz) into source level units (microPa/sqrt(Hz)) so I can make an 'apples to apples comparison?
Thanks





RE: Comparing acoustic data (units question)
I tried to write a quick answer yesterday and it was worse than useless.
I think 2 and 3 are probably identical.
4 may or may not be comparable in any sense with the others.
case 1 is in power like terms, and will increase as 10*log(p1/p0), whereas the others are in volt like terms, and will increase as 20*log(p1/p0)
My basic approach would be to turn them back into Pa^2, and then try and sort the frequency resolution effect out.
Cheers
Greg Locock
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RE: Comparing acoustic data (units question)
Why on earth would someone use 1 uPa instead of 20 uPa as a reference (unless it was in some sort of low pressure environment?
M
--
Dr Michael F Platten
RE: Comparing acoustic data (units question)
1 microPa is typically referenced for acoustic measurements in water.
Greg
Can you explain what you mean by 'frequency resolution effect'. I thought that the /hz and /sqrt(hz) notation was used to normalize the data so band width information isn't needed.
RE: Comparing acoustic data (units question)
- Steve
RE: Comparing acoustic data (units question)
The first principls of course is that sigma v^2 over a given frequency range should be the same, whatever units you are using.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?