Speech–nonspeech detector-classifier

Abstract

The classification of a signal on a telephone line can be based on its short term average energy level; nonspeech (data or signalling) as high level; speech as medium level, and noise as low level. A common use for speech detectors occurs with a time assignment speech interpolation (TASI) system. A speech detector extends a trunk activity signal (TAS) for indicating whether energy or noise is detected on a trunk. Responsive to the TAS signal, a processor processes a signal on the trunk. On occasion, it may be desirable to process different energy signals according to different methodologies. For example, during overload, a TASI system may truncate bits of a speech signal and not truncate bits of a nonspeech signal. For classifying energy signals as between speech signals and nonspeech signals, the instant classifier includes an arrangement for extracting at least one feature, or property, such as the short term power of the signal to be classified. Responsive to the extracted property, an estimator provides a coarse estimate as to whether the signal to be classified is a speech signal or a nonspeech signal. Responsive to the estimate, a six-state, sequency machine provides a fine, classifying signal for classifying the energy signal.