Perception of noise-vocoded speech sounds: Sentences, words, accents and melodies

Recent works on perception of noise-vocoded speech sound (NVSS) have revealed that amplitude envelope information is very important for speech perception when spectral information is not sufficiently available. Basically, the fundamental frequency information is not available and formant peaks cannot not be identified in NVSS. However, we can even recognize accent and distinguish male voice from female voice in NVSS. More, melody can be created from lyrics once lyrics are intelligible. In the present study, findings from fMRI measurement are introduced to show neural activities in the central nervous system during listening to NVSS. The present data indicate that various sites in the brain, which are not ordinarily used for speech recognition, participate in making NVSS intelligible. Applications of the present work include an innovative speech processor and a training system for hearing impaired people.