Voice activity detector
AssigneeBritish Telecommunications public limited company
InventorPaul Alexander Barrett
Life of this patent
Estimating the term…
Abstract
Speech is distinguished from noise by a spectral comparison of an input signal with a stored noise estimate. Updating of the noise estimate stored in a buffer is permitted during periods when speech is absent under control of an auxiliary detector. In order to improve operation in the presence of signals with strong harmonic components, e.g., signalling tones, an LPC prediction gain is computed from the input (x(i)) and a residual (y(i)) obtained from the input following filtering by a filter having a response complementary to the frequency spectrum of the input, and if the gain exceeds a threshold, buffer updating is suppressed.
Claims18
A voice activity detector for detecting the presence of speech in an input signal which comprises a noise component, said detector comprising:
- (a) means for storing an estimate of the noise component of an input signal;
- (b) means for recognizing a spectral similarity of the input signal and the stored estimate to produce an output decision signal;
- (c) means for updating the stored estimate;
- (d) an auxiliary detector arranged to indicate the absence of speech from the input signal and control the means for updating so that updating occurs only when speech is indicated by the auxiliary detector to be absent from the input signal;
- (e) means operable to calculate a prediction gain for the input signal;
- and
- (f) modifying means arranged to suppress said updating of the stored estimate in the event that the prediction gain exceeds a threshold value.
A method for detecting the presence of speech in an input signal which includes a noise component, said method comprising:
- (a) storing an estimate of the noise component of an input signal;
- (b) recognizing a spectral similarity of the input signal and the stored estimate to produce an output decision signal;
- (c) updating the stored estimate;
- (d) using an auxiliary detector arranged to indicate the absence of speech from the input signal and control the updating step so that updating occurs only when speech is indicated by the auxiliary detector to be absent from the input signal;
- (e) generating a prediction gain for the input signal;
- and
- (f) suppressing said updating of the stored estimate in the event that the prediction gain exceeds a threshold value.
Dependencies are inferred from the claim text.