Noise cancelling megaphone

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,
Pete

Hi Pete. I have heard and seen requests like this before but unfortunately I don't think in my opinion anyway that this is not possible because of the multiple sounds thus wave lengths. You may indeed cancel a single tone in one place but it will radiate elsewhere unattenuated. A multiple tone signal like from a jack hammer or drill would have too many sounds to cancel A signal from an inverting amplifier, is not strictly shifting a signal by 180 degrees as that would need a time delay. Thus the amplifier is really a signal inverter. I think that your question could generate quite some interest!