Acoustic information used to determine a user's mouth state which leads to operation of a voice activity detector

摘要

An apparatus and a method for using low-frequency ultrasonic information to improve speech communications, recognition or other processing tasks through determination of mouth state, openness, orientation, proximity, shape and so on. A low frequency ultrasonic signal which can be a chirp pulse train is generated within a device located in the proximity of the mouth, transmitted towards the users face and the reflected acoustic signal is transmitted back from the human face to this or another cooperating device. The received signals are analyzed to determine both time-domain and frequency-domain representations to reveal specific and useful information pertaining to the users mouth state. The system comprises a voice activity detector (VAD) and the information is used to ensure that it only operates when speech is present and not when background noise is present.