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NOISE REDUCTION METHOD BY WHICH A PRIMARY INPUT SIGNAL IS GATED BY A SECONDARY INPUT SIGNAL

IP.com Disclosure Number: IPCOM000004691D
Publication Date: 2001-Apr-07
Document File: 7 page(s) / 1M

Publishing Venue

The IP.com Prior Art Database

Related People

Osman Isvan: AUTHOR

Related Documents

US 5933506: PATENT

Abstract

An improved headset system is described in which voice expansion is applied using a speech level monitor that is essentially noise-free. This is accomplished by incorporating in the headset top, a secondary microphone that is sensitive to the wearer's voice through an internal transmission path, but is insensitive to airborne sound. Voice expansion is done using the signal from the secondary microphone. In a proof-of-concept prototype, this secondary microphone was a piezoelectric disk in contact with the wearer's temple or jawbone.

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NOISE REDUCTION METHOD BY WHICH A PRIMARY INPUT SIGNAL IS GATED BY A SECONDARY INPUT SIGNAL

Osman Isvan, April 4, 2001

Summary

An improved headset system is described in which voice expansion is applied using a speech level monitor that is essentially noise-free. This is accomplished by incorporating in the headset top, a secondary microphone that is sensitive to the wearer's voice through an internal transmission path, but is insensitive to airborne sound. Voice expansion is done using the signal from the secondary microphone. In a proof-of-concept prototype, this secondary microphone was a piezoelectric disk in contact with the wearer's temple or jawbone (see figure 5).

Application

The invention is applicable to communications headsets. In particular, it is of benefit when headsets are used in environments with high background noise; where requirements/expectations for transmit signal clarity and noise immunity are high, or where the signal to noise ratio is low due to limitations imposed on the location of the microphone relative to the wearer's mouth. The invention has special applications in computer headsets used in speech recognition, headsets with short booms, and boomless headsets.

Field of the Invention

This invention relates generally to the field of signal processing to reduce noise. More specifically it relates to the reduction of ambient acoustic noise in the transmit signals of communications headsets. It also relates to the design of contact microphones for headsets to pick up speech signals in noisy environments.

Background

The transmit signal of a communications headset originates at a microphone that is typically located at the end of a boom. The microphone is sensitive to speech as well as unwanted acoustic noise. The signal to noise ratio of the headset is maximized with a long boom that places the microphone close to the mouth of the wearer where the ratio of speech sounds to ambient noise is as high as possible. Microphones that are maximally sensitive along a preferred axis aimed towards the user's mouth (noise canceling microphones) are also utilized. Noise canceling microphones are responsive to pressure gradient and obtain an additional benefit from the proximity effect, and headsets thus equipped achieve the highest signal-to-noise ratios possible for personal communications. However, strong user preference for less weight, shorter booms, boomless headsets, and "earbuds" with in-line microphones that are especially popular in mobile communications applications where ambient noise levels are generally higher, leads to a substantial deterioration of the transmit signal. Consequently, advanced noise reduction techniques including digital signal processing are being increasingly applied to the transmit signals of communications headsets. While this post-processing approach has proven useful, headsets with short booms and boomless headsets still suffer from the limitations inherent in their microphones being exposed to noise.

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