Produce anti-noise

Josiah Carlson jcarlson at
Tue Feb 3 00:55:43 CET 2004

Perhaps I'm not understanding the original question, but if one can get 
the signed (-32768...32767) audio input signals, make it into a numeric 
array (using Numeric or what have you), multiply that numeric array by 
-1, then output the signal, it would be relatively easy to invert the phase.

About the only question is whether or not there is significant overhead 
in reading the audio signal, inverting it, then sending the audio signal 
back to some set of speakers.

Personally, I'm a big fan of the low-tech approach:
Cut the cable in your microphone, swap the wires, seal the cable.

Adjust the volume on your input microphones (for noise cancellation, one 
should optimally have one for each ear), and you are set.

I read an article for doing this kind of thing using just a few 
transistors and a 9V battery to produce a few mW amp and a a pair of 
very small standard microphones in an electronics hobby book in ~1998.

  - Josiah

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