The recognition rate of a speech recognition system is improved by compensating for changes in the user's speech that result from factors such as emotion, anxie ty or fatigue. A speech signal derived from a user's utterance, and a bio-signal, whic h is indicative of the user's emotional state, are provided to a speech recognition s ystem. The bio-signal is used to provide a reference frequency that changes when the user's emotional state changes. An utterance is identified by examining the relative ma gnitudes of its frequency components and the position of the frequency components relativ e to the reference frequency.
SPEECH RECOGNITION USING BIO-SIGNALS