Stealth flier

Friday 15 January 1999

Aeroplane passengers may no longer have to yell at each other to be heard. Ultra Electronics of Cambridge, UK, has designed a passenger seat that halves the perceived ambient noise inside most aircraft cabins.

The trick is done through a sound-cancelling device built into the headrests. A microphone samples sound around the head of the passenger with frequencies up to one kilohertz, including the roar of the engines, the hum of the air conditioners and the 'whoosh' of air along the fuselage.

A signal with the same frequency and amplitude as the incoming noise -- but with the opposite phase -- is then fed to the speakers. The destructive interference between this signal and cabin noise reduces the racket by up to 10 decibels.

"It's perceived by the passenger as less than half of the original din," says Lawrence Earl, spokesperson for Ultra.

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