[music-dsp] Peaks in a wave file

Angelo Farina farina at pcfarina.eng.unipr.it
Wed Jan 7 15:53:00 EST 2004

Use SpectraLab, from Sound Technology (www.soundtechnology.com). You can set
a trigger, having an FFT Spectrum being computed from each pulse, and You
can have the results automatically saved in an ASCII TXT file. You can save
the spectral values, or just the overall SPL, if You like.
Then import the ASCII file in Excel and You will make easily the polar plot.
What I do not understand is why You use 16 loudspeakers... You could have
just employed a single loudspeaker (which ensures that exactly the same
sound is being radiated, it is very difficult to find 2 matched loudpeakers,
16 is surely impossible). Of course, this means that You have to rotate Your
dummy head for each measurement, but this can be easily done with a
turntable. I own a very cheap turntable, produced in Italy by Outline
(www.outline.it). It costed around 600 Euros, can be easily driven by any
computer simply employing the second channel of the sound card, and can give
You polar plots with any angular resolution (down to 2.5 degrees).
You can easily setup SpectraLab for playing a special test signal, which
contains Your burst in the left channels, and a syncronized spike on the
right channel (with proper delay), which is employed for triggering the next
step of the turntable.
Furthermore, as You are using an anechoic chamber, why You do You wait 5s
before the next measurement? 1s should be plenty enough...

Angelo Farina

> -----Original Message-----
> From: music-dsp-admin at shoko.calarts.edu 
> [mailto:music-dsp-admin at shoko.calarts.edu] On Behalf Of Chirag Patel
> Sent: 07 January 2004 22:12
> To: music-dsp at shoko.calarts.edu
> Subject: [music-dsp] Peaks in a wave file
> Hello all,
> I am testing hearing aids in an anechoic chamber.  I am 
> sending a certain frequency pure tone around the hearing aid 
> with 16 speakers towers placed uniformly around the test 
> dummy.  During testing I am playing the pure tones for 1 
> second on each stand and I put a 5 second delay before I 
> change speaker stands.  The dummy has a mic in his ears and 
> is recording the response.  So after each test I have 2 wave 
> files with the response of the hearing aids (Right and Left). 
>  So now I have a wave file and need a sensible way to attach 
> a single numerical value to each 1 second pure tone "pulsed" 
> response and put that on a polar plot.
> Does anyone have any ideas as to how I can do this?
> Thanks,
> Chirag
> ******************************
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> Chirag Patel
> National Centre for Audiology
> cpatel at nca.uwo.ca
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