Tuesday, May 20, 2014
Loud can be dangerous
Fortunately, I've suffered little hearing loss in my flying career, partially because I've been religious about wearing the best active noise reduction headset I could find since ANR became available to the pilot public.
My first ANR headset was a David Clark with a separate battery box that required me to carry large quantities of AA batteries all over the world. A fresh set of AA batteries was good for about four hours, so a typical 10- to 12-hour leg across the Atlantic or Pacific demanded several cards of batteries.
As most pilots know, ANR isn't a terribly complex solution to noise pollution. A simple one-dimensional ANR system consists of a microphone and speaker that analyzes sound coming into a headset and transmits a waveform that's exactly counter to the noise source, effectively cancelling most of the offending sound.
ANR is most effective at nulling low-frequency sound, and the technology has been around since the 1950s. One of its most publicized practical applications was on the round-the-world, unrefueled trip by Dick Rutan and Jeana Yeager in Voyager in 1986. Bose provided experimental headsets for the two pilots on their unrefueled circumnavigation of earth.
Since then, ANR has been developed to lighter and more efficient designs that have progressively come to attenuate both aircraft noise and any other form of noise pollution. Today, you can buy receive-only ANR headsets for as little as $100 that will suppress sound levels in all manner of machines.
The technology has advanced significantly in the last 30 years, and today, there are several headset manufacturers that produce sets that offer as much as a 25 to 30 dB reduction for as long as half a day. A few manufacturers even allow tying in to aircraft power for unlimited noise attenuation.
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