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Produce anti-noise

David Konerding dek at compbio.berkeley.edu
Mon Feb 2 18:44:26 EST 2004 
In article <bvmlik$kam$06$1 at news.t-online.com>, Diez B. Roggisch wrote:
>> I want to know if the is a way to do something in python to produce
>> some anti-noise (i.e. I talk in the microphone and the sound go out by
>> the speakers but with inversed phase).
>> 
>> So I want to know how to control the microphone and to add some sort
>> of effect to the sound that enter in and to put it out with that
>> effect and all this at the same time.
> 
> AFAIK such things need vast amounts of computational power for very
> complicated algorithms and very low latencies - a job for specialised DSP
> code. Its much more complicated than inverting the amplitude (I don't think
> that inverting the phase is possible - AFAIK you can only shift it, and
> thats not what you want here...)
> 
> So I seriously doubt that you can do that with python - I even doubt that
> you can do it with you computer. Not so much from the raw computational
> power side of the thing, but much more from your audio-equipment.
> Professional noise reduction systems costs several thousands of euro and
> feature lots of speakers, especially designed, chosen and arranged to
> reflect the acoustic envrionment of _one_ room, e.g. the inside of a
> certain car. Then specially adapted algorithms come into play.

Hmm.  You can buy a $200 set of bose headphones that do it with a simple chip and low power.
I think a regular PC could do this (so long as you know the equations) by brute force.  You'd probably want to 
use signal processing libraries rather than pure Python, though.
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