How to Detect Speech in Telephone Dialogue Systems

In practical telephone dialogue applications there are many problems with a speech detection. This paper discusses two main problems with a silence detection and presents techniques for increasing reliability and recognition accuracy of the whole telephone dialogue system. The first problem causes a different level of signal and background noise of incoming calls. The solution could be to store the local speech/silence decision in a buffer and to use an adaptive threshold to make a global decision about each frame. The second problem is the detection of the spoke-too-soon error and its recovery. In addition this paper describes a dialogue system with a speaker independent recognition module for Czech continuous speech. The recognition module has been designed at the University of West Bohemia (UWB) and is used for telephone applications. The task of this module is to recognize and transcribe continuous Czech telephone speech to a word sequence restricted by a stochastic regular grammar.