ACOUSTIC PROXIMITY DETECTION VOX EMPLOYING TWO MICROPHONES

IP.com Prior Art Database Disclosure
IP.com Disclosure Number: IPCOM000007432D
Publication Date: 01-Jul-1995
Find Similar Download

Publishing Venue

Motorola Technical Bulletins

Related People

Clint Luckinbill - Author

Abstract

The VOX described here is an audio proximity detector. Applications for the VOX are envisioned as supportive of portable radio communications. Two microphones are utilized. The 1st is placed next to the VOX operator's mouth to capture his voice and the 2nd placed away from his mouth to capture back- ground noise. Differences in the microphone sig- nals are used to discern when the VOX operator is talking. Environments benelitting from this design are those incorporating human voices in the back- ground noise. Imagine the difficulty in getting a nor- mal VOX to operate a portable radio at the ball park. A noisy environment filled with loud voices makes it difficult to discern the operator's voice from the background. The VOX described here has no difft- culty in these environments as it discerns ambient sounds as distant relative to the operator mouth.

Copyright

Motorola Inc. July 1995

Language

English (United States)

Country

United States

Document File

2 pages / 133.8 KB

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 50% of the total text.

Page 1 of 2

0 M

MOlVROLA Technical Developments

ACOUSTIC PROXIMITY DETECTION VOX EMPLOYING TWO MICROPHONES

by Clint Luckinbill

INTRODUCTION

  The VOX described here is an audio proximity detector. Applications for the VOX are envisioned as supportive of portable radio communications. Two microphones are utilized. The 1st is placed next to the VOX operator's mouth to capture his voice and the 2nd placed away from his mouth to capture back- ground noise. Differences in the microphone sig- nals are used to discern when the VOX operator is talking. Environments benelitting from this design are those incorporating human voices in the back- ground noise. Imagine the difficulty in getting a nor- mal VOX to operate a portable radio at the ball park. A noisy environment filled with loud voices makes it difficult to discern the operator's voice from the background. The VOX described here has no difft- culty in these environments as it discerns ambient sounds as distant relative to the operator mouth.

purpose of detecting a local voice. The 1st micro- phone is an accessory microphone, common in port- able radio VOX applications, that is positioned near the operator's mouth. The 2nd microphone, the radio's internal microphone which is normally disa- bled when the accessory microphone is present, is located away from the operator's mouth. The inven- tion uses the 2nd microphone to sense the ambient noise level and maintain a threshold for VOX activation.

  Operator adjustment of the VOX to compensate for the environment is not necessary. The 1st micro- phone acquires the operator's voice and the 2nd microphone acquires an attenuated version. Both microphones detect the audible environment. The operator's voice produces a SPL differential across the microphones. VOX activation is dependent on the differential's magnitude. The separation and positioning of the microphones define the perform- ance of the VOX.

DESCRIPTION

This invention utilizes two microphones for the

1ST MICREOQPUH; SIGNAL OPERATOR'S VOICE AUDIBLE EhIRONMENT >

2ND MICREod;$E SIGNAL ATTENUATED OPERATOR'S VOICE

AUDIBLE EiiVIRONMENT >

Fig. 1 VOX Block Diagram

0 2IOI"dil. Inc. 1995

42 July IY95

[This page contains 15 pictures or other non-text objects]

Page 2 of 2

MOlVROLA Technical Developments

  Initial desires were to operate the VOX from a signal stripped of background noises, containing only the operator's voice. The signal from the 1st micro- phone, primarily containing the operator's voice, would be stripped of the ambient sounds primarily found in the signal provided by the 2nd microphone.

  Activating a VOX with a signal which is only the operator's voice requires only one activation threshold. Adjustments required to contend with var- iations in background noise are not required since it has been removed.

  Implementing this process requires complex adaptive filters and produces results beyond those needed for the VOX. Sufficient emulation of the adap- tive filters resultant output can be produ...

First page image
There may be a charge to download this document but you are authorized to receive it free.
Files available for download:
  • a representative PDF of the primary file (contains all the relevant information for most users)
  • the full document ZIP file containing the primary file, packaged metadata, and attachments (as appropriate)
To obtain the file, please enter the "captcha" below and click the Download button.
Avoid entering CAPTCHAs! Sign In or Create a Free Account.

Challenge image
  • Please enter letters and numbers only; no spaces.
  • Cannot read this one? Click the image.
  • Difficulty with captchas? Contact us with the URL of this page and we will email it to you.