Assessing the importance of several acoustic properties to the perception of spontaneous speech.

Spoken language manifests itself as change over time in various acoustic dimensions. While it seems clear that acoustic-phonetic information in the speech signal is key to language processing, little is currently known about which specific types of acoustic information are relatively more informative to listeners. This problem is likely compounded when considering reduced speech: Which specific acoustic information do listeners rely on when encountering spoken forms that are highly variable, and often include altered or elided segments? This work explores contributions of spectral shape, f0 contour, target duration, and time varying intensity in the perception of reduced speech. This work extends previous laboratory-speech based perception studies into the realm of casual speech, and also provides support for use of an algorithm that quantifies phonetic reduction. Data suggest the role of spectral shape is extensive, and that its removal degrades signals in a way that hinders recognition severely. Information reflecting f0 contour and target duration both appear to aid the listener somewhat, though their influence seems small compared to that of short term spectral shape. Finally, information about time varying intensity aids the listener more than noise filled gaps, and both aid the listener beyond presentation of acoustic context with duration-matched silence.