US 4,357,491 A · Method of and apparatus for detecting speech in a voice channel signal

Abstract

Speech signal presence is decided based on the input signal exceeding either of two thresholds: one, a fixed threshold (TF) set at an arbitrary level relatively high above anticipated noise; the other, an adaptive threshold (TL) which idles slightly above noise. If the input signal rises above the idling threshold of TL, speech presence is indicated. If the input signal continues to rise (i.e., amplitude-time slope positive), the presence indication continues. If the input signal level falls, the adaptive threshold is adjusted (TL=BT+D, where for example B=1, D=5 and T=the current signal sample average value). Hangover is controlled by the amount of time the input signal exceeds the threshold TL. Speech presence is also indicated by the input signal exceeds a third threshold (TH) which is also adaptive, and idles at a relatively high level above noise.

Claims13

Dependent claims

A method of detecting the presence of speech signals in a sampled voice channel signal, comprising the steps of:

producing a first signal state whenever the magnitude of a signal sample exceeds a first threshold level;
comparing the magnitude of each sample with that of the preceding sample;
whenever the magnitude of a sample is not greater than that of the preceding sample, setting a second threshold to a level which is greater than and is dependent upon the magnitude of the current sample;
whenever the magnitude of a sample is greater than that of the preceding sample, producing a second signal state if the magnitude of the current sample exceeds the second threshold;
and
in response to each of the first and the second signal states, producing a signal, representing the presence of speech, at least in respect of the current sample.

3 more elements

Dependencies are inferred from the claim text.

Method of and apparatus for detecting speech in a voice channel signal

Life of this patent

Method of and apparatus for detecting speech in a voice channel signal

Life of this patent

Abstract

Claims13