British Telecommunications Public Limited Company

Neil Robert Garner

Paul Alexander Barrett

A voice activity detector suitable for deployment in a mobile phone apparatus is disclosed. An advantage of the voice activity detector is that it is better able to provide a decision ( ) as to whether an input signal ( ) consists of noise (which it is not desired to transmit) or comprises speech or information tones (which are required to be transmitted), especially in noisy environments. The voice activity detector includes a number of components, in particular an auxiliary voice activity detector ( ). The auxiliary voice activity detector ( ) distinguishes between noise and speech on the basis that the spectrum of speech changes more rapidly than that of noise. This results in the auxiliary detector ( ) rarely mistaking a speech signal to be a noise signal. Hence, a very reliable noise template ( ) is obtained. For this reason, the auxiliary detector ( ) is also useful in noise reduction applications. The voice activity detector also uses a neural net classifier ( ).

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Walsall, United Kingdom

Neil Robert Garner