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Noise cancelling megaphone Answered

Hello all:)
I was wondering if I could get some help and advice about a project I've had in mind for a while.
The idea is to use a modified electronic megaphone to produce sound that's antiphasic of the microphone input.
I want to keep the execution as simple as possible to retain signal quality and keep it something I might be able to do myself with a little studying up. I got the idea when I noticed if you incorrectly wire a couple speakers one can produce output that's 180 degrees out of phase, cancelling most of the sound emitted.
Ultimately I'd like to use the device to help quiet the sounds of the power tools I use as a favor to my neighbors and to save my hearing a bit:) This should be doable since I could keep the megaphone near the source.
Thanks a bunch for any help,


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8 years ago

You might possibly be interested in phase conjugation or time-reversed signals.

However, for your case, I don't think you're going to be successful. The problem is that the sound doesn't propagate cleanly through air. It is reflected, refracted, conducted through solids (like windows) and retransmitted. Even if you phase-conjugate the sound within your workshop, that probably wouldn't do as much outside as you might think.

To save your own hearing, you should be wearing properly rated hearing protection. Those headphones explicitly absorb and dampen the sound, preventing the acoustic energy from reaching your ears.

For your neighbors, is your workshop large enough that you can keep doors closed and add some wall insulation?