Produce anti-noise

[Phil Hornby]

The big problem with this sort of thing is latency - DSPs have a very low
latency as they are generally designed to do 1 operation per cycle and their
sole purpose is to do the signal processing not worry about all the other
stuff a normal PC has to worry about - i.e. the OS. Most solutions that run
on a desktop machine would have a dedicated DSP on a PCI card and would NOT
run on your PC's main CPU as it is not a simple processing power
issue...more a round trip delay issue... and getting through an OS and an
Interpreted language would most likely be too much delay... It might be
possible to do it by wrapping a C API to a Commercial DSP system that would
allow you to configure the hardware to do what you want...

HTH

--
Phil

"Requirements - what are they I just hack something together that does what
I think they want" ;)

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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