noise canceling, out of phase, antiphase

I am trying to use Audacity to take a short wav file and run a filter on it to create its negative or anti. Similar to noise canceling. I then want to play back the original wav and the new filtered / anti wav and see if they really cancel each other out. I have played with the phaser filter but Im not sure it is the filter I need. Can anyone tell me if this is the correct filter to accomplish this? What filter should I use?


Hmm. I found it! I used Invert from the Effect menu. Now how can I do that realtime with the mic in and make my surround sound cancel out all sound that meets certain patterns like “Take the garbage out. Make your bed.”, no seriously though.

In order to invert the mic signal (though why you’d want to do this is beyond me), just cut open the cable and swap the two non-ground wires.

Don’t actually do that though, it’s pointless.

If you want to avoid hearing something, soundproof the door. Selective sound canceling a la Minority Report (the film, not the short story) is well beyond our current level of technology.

I am only interested in canceling out sound of the frequency 1100 to 1220 hertz that lasts approx 1/20 of a second and repeats every 2 seconds.


Is this another hypothetical question? If it isn’t, are you trying to do this in realtime, or are you trying to cancel out an unwanted noise in a recorded file?

You can do that as long as you’re trying to cancel it out of an already existing file, and the sound is regular (exactly the same amount of time between each occurance, not “about 2 seconds or so”). But you have to have access to a “clean” sample of that sound. If it’s something that shows up on your recordings, try recording silence and see if it’s still there.

Once you have a clean copy of that sound, it’s a simple matter of lining up the waveforms, adjusting the gain on each, and inverting one of the soundfiles.