Envelope information in speech processing: acoustic-phonetic analysis vs. auditory figure-ground segregation

Long-term envelope modulations (< 100Hz) influence the identification of speech in noise. It is not clear, however, whether this influence only takes place at the level of acoustic-phonetic analysis (phonetic identification) or if envelope fluctuations may also help in auditory figureground segregation (e.g. separation of speech from concurrent backgrounds). An experiment is presented in which the influence of long-term envelope modulations was investigated using signals mixed with either stationary or temporally modulated noise. The better performance observed when processing speech in modulated background may be related to the listeners’ ability to use envelope information in trying to follow concurrent signals independently. It is therefore predicted that, if longterm envelope modulations help to segregate speech from noisy backgrounds, this effect should be stronger when envelope information is fully available.