Browse Prior Art Database

Voice Activity Detector

IP.com Disclosure Number: IPCOM000045190D
Original Publication Date: 1983-Feb-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 2 page(s) / 24K

Publishing Venue

IBM

Related People

Crauwels, GL: AUTHOR [+3]

Abstract

This device provides an improved method of detecting voice activity which eliminates most of the analog signal conditioning circuitry associated with earlier detection schemes (1). This is accomplished by using the high speed computing power available in microprocessors and a simple analog detector.

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Voice Activity Detector

This device provides an improved method of detecting voice activity which eliminates most of the analog signal conditioning circuitry associated with earlier detection schemes (1). This is accomplished by using the high speed computing power available in microprocessors and a simple analog detector.

The AC-coupled voice signal is converted to a digital signal by the analog detector shown in the drawing. The voice signal is applied at 1. Capacitor 2 is selected to present an impedance which is low enough at operating frequencies to block any signals from reaching the comparator 3 input. Resistors 4-6 are calculated to meet the following requirements: 1. Resistors 4 and 5 set the threshold level that switches

comparator 3.

2. Resistor 6 sets the comparator input bias level.

3. Resistor values are selected to minimize loading of input

signal 1 and minimize bias offset effects of comparator 3.

When no input signal is present and VB is positive, comparator 3 output 7 is at a negative level, because input line 1 is more positive than comparator positive input 9, by the bias across resistor 5. When the input signal goes negative a greater amount than this bias, the comparator output will switch positive. This output will remain positive as long as input line 1 is more negative than the comparator input 9. Since both comparator inputs are biased from the same source, little drift in threshold occurs and circuit sensitivity is extremely stable.

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