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Old 25th March 2006, 01:44 AM   #1
deandob is online now deandob  Australia
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Default software 1/3 octave pink noise generator

Hi,

Does anyone know of any software that can create 1/3 octave pink noise tones for speaker frequency SPL testing. I have had a good look around this site & the 'net and can find heaps of sine tone generators but not pink noise software generators. I have Cool Edit 96 that can create pink tones but I can't work out how to do 1/3 octave filtering.

Even downloads of 1/3 octave pink tones would be fine.

Regards,
Dean
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Old 25th March 2006, 02:40 AM   #2
GM is offline GM  United States
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Greets!

http://www.sonicspot.com/wavetools/wavetools.html

GM
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Old 25th March 2006, 03:25 AM   #3
deandob is online now deandob  Australia
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Hi GM.

A couple of handy utilities there. I checked out the pink noise function in the generator and it looks like it uses a pre-generated pink noise wav file and you cannot select the frequency band, even when you use the menu to select the centre frequency.

Regards,
Dean
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Old 25th March 2006, 04:48 AM   #4
deandob is online now deandob  Australia
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I found this while searching the 'net:
http://www.moshier.net/pink.html

Will generate a WAV file using pink noise band limited to 1/3 octave spread over 30 frequencies. Dump the PCM into cooledit and extract the various frequencies (12 seconds each) into separate WAV files and away I go.

What a difference using these files versus simple sine waves at specific frequencies. The sine waves would have the soundmeter bouncing all over the place depending on location & frequency, yet I get a much more consistent response using the 1/3 octave WAV files and can finally see the response of my speakers.

Regards,
Dean
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Old 25th March 2006, 05:08 AM   #5
GM is offline GM  United States
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Greets!

Pink noise is for displaying a speaker's response, hence the generator's 20-20 kHz BW, which BTW is centered around 630 Hz (~632.45 Hz actually) and not the 1 kHz checked, so why would you want a 1/3 octave pink tone? I mean the spacing just defines the response resolution.

Anyway, if you can make them in Cool Edit, then you can calc their BW:

Fh = Fl*2^n

Fl = Fh/2^n

where:

Fh = upper frequency
fl = lower frequency, or the XO point in this case
n = octave spread

So if you want to start at 100 Hz, then 1/3 octave on either side is:

Fh = 100*2^1/3 = ~126 Hz

Fl = 100/2^1/3 = ~79.4 Hz

GM
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Old 25th March 2006, 06:46 AM   #6
deandob is online now deandob  Australia
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Hi GM,

I have just built a pair of Jordan JXR6 HD monitor speakers and was not happy with the hollow sound. I wanted to frequency equalise the speakers (for BSC & room modes).

After using a graphic equaliser and a sound level meter with the 1/3 pink octave tones over the speaker bandwidth the in room response is much better and the sound is richer now!

Regards,
Dean
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Old 25th March 2006, 07:05 AM   #7
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There's WinAmp/XMMS plugins to generate defined noise of all sorts too
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