The voice activity detector for the Pan-European digital cellular mobile telephone service

A description is given of the voice activity detector (VAD) standardized by CEPT for use in the Pan-European digital cellular mobile telephone service. The speech-coding algorithm chosen is a 13-kb/s speech coder, using a technique in which speech is produced at the decoder by passing a substitute for the residual through long-term and short-term predictor filters. The difficulties of detecting speech in a noisy environment are discussed, and the performance tests carried out to validate the design are described. The tests show that clipping levels are very low but that low levels of speech activity are recorded in conversations. The VAD has low complexity (because it uses the results of analysis performed in the speech coder) and is failsafe in difficult conditions