Headphones That Turn Down The Volume On Excess Noise

Amar bose was frustrated. It was 1978, and he’d planned to kill some of the time on his 6000 km flight from Zurich to Boston by listening to music through some new, foam-covered (read: flimsy) headphones that Swissair supplied to the passengers. His enjoyment was foiled by the drone of the engines, which overpowered the lightweight headset.

- Jim Allen

Fortunately, Bose was a professor of electrical engineering at MIT, and the head of his own electronics company, the Bose Corporation. By the time he had arrived in Boston, he had scrawled the first steps towards a solution to his sonic problem: noise-canceling headphones.

The idea had precedent – scientists such as Lawrence J Fogel in the ’50s and Paul Lueg in the ’30s had applied for patents on their own versions of the concept, for use in everything from concert halls to helicopters. But Bose came to the idea independently. And nobody had put the pieces together in a way that would work for consumer headphones.

‘In order to cancel a noise,’ says Dan Gauger, a member of the original engineering squad Bose put together to realise his vision, ‘you have to take all frequencies. For each one of those, you have to make a noise at the same frequency, of the same amplitude, but the opposite phase. So you have to combine a +1 with a –1.’ To accomplish this, and make the technology workable enough for mass use, Bose’s team incorporated a couple of crucial innovations of the ’70s, like a small electret microphone. It was composed of high-resistance material providing a permanent charge without needing a ton of voltage and current. Positioned near the entrance to the ear canal, the electret mic picks up sound so the circuitry can compare the noise outside the headphones to what you want to hear – your music – and produce that opposite phase sound. Then, you hear only the tunes.

Anyone who’s watched a school principal struggle with an oversaturated microphone and an ancient PA system knows feedback can be a nuisance when it’s accidentally generated. But when it’s tailored to zap unwanted noise, it can be your best friend.