US 6,640,208 B1Granted

Voiced/unvoiced speech classifier

AssigneeMotorola, Inc.

InventorsYaxin Zhang, Jianming Song, Anton Madievski

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Abstract

A voiced/unvoiced speech classifier (30) includes a speech segmentor (34) which segments an input digitized speech waveform into frames of speech and a band-pass filter (36) which filters the frames of speech. A relative energy generator (38) generates a relative energy value for each filtered frame of speech and a decision parameter generator (52) including an autocorrelation calculator (54) and a pitch calculator (56) generates a decision parameter based on an autocorrelation function and a pitch frequency index for the filtered frames of speech. A normalized energy calculator (46) adjusts the threshold and then normalizes the relative energy. A comparator (60) provides a signal indicative of whether a frame of speech is voiced speech or unvoiced speech depending on a comparison of the decision parameter and the normalized relative energy value for each filtered frame of speech.

Claims17

Dependent claims

A voiced/unvoiced speech classifier comprising:

an input terminal for receiving a digitized speech signal;
a feature extractor having an input coupled to the input terminal and an output providing feature vectors of the input speech signal;
a correlator having an input coupled to the output of the feature extractor and an output providing an autocorrelation value of the feature vectors of the input speech signal;
a decision maker having a first input coupled to the output of a combiner, a second input for receiving a threshold value and an output providing a signal indicative of whether a measure of the input speech signal partly based on the autocorrelation value of the feature vectors of the input speech signal is above or below the threshold value;
a Signal to Noise Ratio (SNR) calculator having an input coupled to the input terminal and an output providing a SNR signal;
a threshold value adjuster having an input coupled to the output of the SNR calculator and an output coupled to the second input of the comparator to provide thereto the threshold value adjusted according to the SNR signal;
a signal energy calculator having an input coupled to the input terminal and an output providing an indication of the energy of the input speech signal;
and
a combiner having a first Input coupled to the output of the correlator, an output coupled to the first input of the comparator and a second input coupled to the output of the signal energy calculator providing the measure of the input speech signal.

6 more elements

Dependencies are inferred from the claim text.