Psycho-acoustics and Speech Perception

Computational models of speech pattern processing might be able to benefit a lot from sound and speech perception by humans. Psycho-acoustics has given us insight into the limits and the capabilities of peripheral hearing for, mainly, simple stationary sounds. Threshold phenomena and temporal and spectral resolution for such stimuli are a first indication of how the front end of a recognizer should be modeled, and what level of precision is required in rule synthesis. Much less is known about the ear’s sensitivity to dynamic events with complex signals, such as formant-like transitions. Once the signal becomes a syllable or a meaningful word or sentence, our ear’s behavior and our brain’s interpretations become even more complex. A good example of that is our perception of stressed and unstressed syllables, including schwas. I will claim that vowel reduction manifests itself as contextual assimilation, rather than as a form of centralization, which again has implications for our phone and word models in ASR and for our coarticulation rules in a synthesizer.