IUBio

Zwicker effect

r norman rsnorman_ at _comcast.net
Mon Jun 2 09:22:42 EST 2003


My impression of the simplest way of doing this would be to create a
random white noise file digitally.  Fourier transform it and do a
sharp cutoff on the high frequency end.  Inverse transform it to
generate a wav file.

Once you have done all the hard programming work, it would be trivial
to play with band widths.  Of course, a well-equipped auditory
psychophysics (or sensory physiology) lab would probably already have
a white noise generator and good sharp filters and you could just
twiddle the knobs to play with it!

I'd try it, except my own auditory apparatus already has its own very
sharp cutoff around 5 kHz.  Not to mention the constant tinnitus that
prevents me from recognizing a faint high frequency tone!


On 2 Jun 2003 00:48:14 -0700, tonyjeffs at aol.com (TonyJeffs) wrote:

>r norman <rsnorman_ at _comcast.net> wrote in message news:<8qmkdv0uonkb8lh4bvdqofnk7873furd2j at 4ax.com>...
>> I don't know whether it will work or not but, judging from some basic
>> neurophysiology of hearing, it is likely to require that the cutoff be
>> at a rather high frequency, at least several kHz.  
>> 
>> What frequencies have you been trying?  How sharp is your cutoff?
>> (are you using digital or analog filtering?)
>> 
>> 
>
>
>Just dabbling with shareware on the PC.
>Take your point - I think I need to go into a lab and do it properly.
>
>But dabbling made me think about it. It's some 20 years since I was a
>student in an acoustics lab, and it struck me that it would've been a
>great demo for the class, but they didn't do it.
>
>I'm going to try and do it. Hardest part is getting permission to use
>equipment
>
>Here's a thought:- 
>I imagine noise from 25hz to 5000hz at 40dB, with >60dB/oct rolloff
>sounds about right to work.
>What if we raise the lowes frequency;  100hz to 5000 hz?  yup probably
>What about  500hz to 5000hz?
>What about   2500 to 5000
>
>- I wonder how wide the noise band needs to be!
>
>Thanks
>
>Tony




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