Bose markets a pair of super-expensive noise-cancelling earphones that they target at frequent air travellers and such. I assume they work on the same principle as standard aeronautical noise-cancelling headsets and the Blue Thunder spy helicopter: they have a microphone pickup which senses the ambient sounds in the area, and a speaker which generates a tone of opposite frequency and amplitude (?). The two combine in the space between the headset and your ears and cancel each other out. voila: silence thru extra noise.

A lot of laptops have built in microphone pickups now, and virtually all personal computers come with a line in jack, into which a cheap mass-manufactured videoconferencing style mic could be plugged. I wonder how hard it would be to write a program to measure the incoming audio from the line in plug and generate a noise cancelling signal to output to headphones. And I wonder how well that would work given non-enclosure style headphones. Obviously it would only work when you were sitting at a computer, but there are plenty of computer-sitting times when I would like a little silence for better concentration.

Hmmm.