For a story I was writing about 20 years ago, I dreamed up this idea: why not take a set of microphones and a PA speaker/amplifier setup and interpose some phase-shift/delay circuitry to create a DIY noise cancellation system? It might not be acoustically perfect, but it would damned sure do something cool. A few years later, Saab and Volvo started building this into their car audio systems and Bose started putting it in headphones. I’m sure I stole the idea from Arthur C. Clarke or Popular Science, so I never bothered to try to collect royalties. Now, finally, there’s this article telling you how to do it (for headphones at least). I really want to build this, connect it to about 5000 watts of amps and a cloud of speakers, and silence my whole neighborhood (from my perspective anyway).