ASSESSING THE EFFICACY OF ACTIVE NOISE REDUCTION (paper presented at Defence Science Symposium, Ottawa, Ontario, Canada, 25 - 26 April 1990)

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Authors
  1. Rylands, J.M.
Corporate Authors
Defence and Civil Inst of Environmental Medicine, Downsview ONT (CAN)
Abstract
Active noise reduction (ANR) is an electronic technique for reducing low frequency noise reaching the operator's ears. It works on the principle of reverse phase cancellation. First, noise entering the earcup of a flight helmet, headset or ear defender is sensed using a miniature microphone. The signal from the microphone is then passed through a phase compensation filter which reverses the phase. This antiphase noise is amplified and passed back into the earcup through the helment or headset transducer and then cancels the source waveforms. The low frequency component of any speech signal passed along the communication line is similarly affected by the ANR unless a speech pre-emphasis circuit is used to counteract this.
Date of publication
15 Apr 1990
Number of Pages
6
DSTKIM No
90-03678
CANDIS No
65921
Format(s):
Hardcopy;Originator's fiche received by DSIS;Document Image stored on Optical Disk

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