A DYNAMIC EAR-INSERT NOISE REDUCTION SYSTEM

Authors
Corporate Authors
Defence and Civil Inst of Environmental Medicine, Downsview ONT (CAN);Bell-Northern Research Ltd, Ottawa ONT (CAN)
Abstract
An active system for noise-reduction in the ear canal has been developed, for safer and more reliable speech communication in noisy environments. Contrary to passive, bulky ear defenders, which require mass to provide more and more sound insulation between the noisy environment and the ear canal, this system is characterized by reduced size and weight. It utilizes an era-insert together with an active, negative feedback loop. The loop consists mainly of an active filter, which provides a frequency-dependent amplification and phase-shift for the noise signal, detected from the ear canal by a miniature microphone. The modified noise signal is fed back to the ear canal through a miniature receiver, thus providing "negative" noise of equal magnitude which "cancels" the original noise. The receiver and the miniature microphone, form an integral part of the ear-insert. The receiver is also used to feed the intelligence or message signal to the ear canal. The circuitry does not influence the message signal, either in magnitude or in phase. The described system gave a noise "cancellation" of up to 10 dB in the frequency range of 100 to 3200 Hz, i.e. the range of speech communication. Thus an improvement of 10 dB in signal-to-noise ratio can be realized for communication purposes. In addition, the noise level at the ear is similarly reduced for safer operation.
Date of publication
01 Sep 1979
Number of Pages
76
DSTKIM No
93-04237
CANDIS No
133800
Format(s):
Hardcopy;Originator's fiche received by DSIS

Permanent link

Document 1 of 1

Date modified: