Voice activity detection system, method, and program product

A speech processing method for processing a speech by a computer device, the method comprising the steps of:

• dividing an input speech signal into frames, wherein said input speech signal is received from a voice activity detection apparatus;
• converting said input speech signal to a logarithmic power spectrum;
• performing long-term spectrum variation component extraction to generate a first feature vector by steps of:
• transforming said logarithmic power spectrum to mel cepstrum coefficients;
• and
• extracting a long-term spectrum variation component from a sequence of said mel cepstrum coefficients by linear regression calculation using a longer delta window than an average phoneme duration of an utterance in said input speech signal to generate a first feature vector;
• performing harmonic structure feature extraction to generate a second feature vector by steps of:
• transforming said logarithmic power spectrum to cepstrum coefficients by a discrete cosine transform;
• cutting off upper and lower cepstrum components from said cepstrum coefficients;
• inverse discrete cosine transforming said cepstrum coefficients from which said upper and lower cepstrum components have been cut;
• converting an output of said inverse discrete cosine transform back to a power spectrum;
• mel filter bank processing said power spectrum to produce mel filter bank processed output;
• and
• transforming said mel filter bank processed output to a second feature vector comprising a harmonic structure feature by said discrete cosine transform, and
• determining a voiced segment by using said long-term spectrum variation component first feature vector concatenated with said harmonic structure feature second feature vector and comparing the concatenated feature vectors to a statistical model,
• wherein at least one of the steps is carried out using the computer device.

A speech processing program product tangibly embodying computer readable non-transitory instructions which, when implemented, causes a computer device to perform the steps of:

• dividing an input speech signal into frames, wherein said input speech signal is received from a voice activity detection apparatus;
• converting said input speech signal to a logarithmic power spectrum;
• performing long-term spectrum variation component extraction to generate a first feature vector by steps of:
• transforming said logarithmic power spectrum to mel cepstrum coefficients;
• and
• extracting a long-term spectrum variation component from a sequence of said mel cepstrum coefficients by linear regression calculation using a longer delta window than an average phoneme duration of an utterance in said input speech signal to generate a first feature vector;
• performing harmonic structure feature extraction to generate a second feature vector by steps of:
• transforming said logarithmic power spectrum to cepstrum coefficients by a discrete cosine transform;
• cutting off upper and lower cepstrum components from said cepstrum coefficients;
• inverse discrete cosine transforming said cepstrum coefficients from which said upper and lower cepstrum components have been cut;
• converting an output of said inverse discrete cosine transform back to a power spectrum;
• mel filter bank processing said power spectrum to produce mel filter bank processed output;
• and
• transforming said mel filter bank processed output to a second feature vector comprising a harmonic structure feature by said discrete cosine transform, and
• determining a voiced segment by using said long-term spectrum variation component first feature vector concatenated with said harmonic structure feature second feature vector and comparing the concatenated feature vectors to a statistical model.

A speech output system for outputting a speech entered from a microphone by a computer, the system comprising:

• (1) means for converting said speech entered from said microphone into a digital speech signal by ND conversion;
• (2) means for dividing said digital speech signal into frames;
• (3) means for converting said digital speech signal divided into frames to a logarithmic power spectrum;
• (4) long-term spectrum variation component extraction means comprising:
• transform means for transforming said logarithmic power spectrum to mel cepstrum coefficients;
• and
• extraction means for extracting a long-term spectrum variation component from a sequence of said mel cepstrum coefficients by linear regression calculation using a longer delta window than an average phoneme duration of an utterance in said speech signal, said long-term spectrum variation component comprising a first feature vector for the frame;
• (5) harmonic structure feature extraction means comprising:
• discrete cosine transform means for transforming said logarithmic power spectrum to cepstrum coefficients by a discrete cosine transform;
• clipping means for cutting off upper and lower cepstrum components from said cepstrum coefficients;
• transform means for inverse discrete cosine transforming said cepstrum coefficients from which said upper and lower cepstrum components have been cut;
• conversion means for converting an output of said inverse discrete cosine transform back to a power spectrum;
• processing means for mel filter bank processing said power spectrum;
• and
• harmonic structure transform means for transforming a mel filter bank processed output to a harmonic structure feature by said discrete cosine transform, to generate a second feature vector for each frame, the second feature vector comprising the harmonic structure feature;
• (6) means for determining a voiced segment by concatenating the first feature vector from said long-term spectrum variation component means and the second feature vector from said harmonic structure feature means and comparing the concatenated feature vectors to a statistical model;
• (7) means for discriminating speech and non-speech segments in said digital speech signal by using said voiced segment information;
• and
• (8) means for converting said discriminated speech included in said digital speech signal into said speech as an analog speech signal by D/A conversion.