Listeners are often required to attend to speech in background noise. Coherent prosodic structure has been found to facilitate speech processing (Cutler, Dahan & Donselaar, 1997). The aim of this thesis is to investigate to what extent these prosodic cues, in particular fundamental frequency (FO), aid speech intelligibility in noise. Experiments measured Speech Reception Thresholds for sentences with different manipulations of their FO contour. These manipulations involved either a scaled reduction in FO variation, or the complete inversion of the FO contour. Experiments reported in Chapter 2 investigated the impact of these FO manipulations against speech-shaped noise and single-talker interferers. Inverting the FO contour was found to significantly degrade target speech intelligibility for both types of interferer, although a larger effect was observed with the single-talker interferer. No effect of altering the FO contour of the interferer was found. Low-pass filtering the FO contour (Chapter 3) showed that the most important frequencies lay at or below the syllable rate of speech, highlighting the importance of syllabic and suprasegmental fluctuations within the FO contour. Experiments in Chapter 4 compared synthesised and natural targets. Synthesised speech was found to be considerably less intelligible than natural speech. No consistent effect of FO inversion was noted for synthesised FO contours. However neither natural FO nor duration contours improved the intelligibility of the synthesised speech. Similar experiments using non-native English speakers (Chapter 5) showed a greater detriment to the perceived intelligibility of the speech with FO manipulations than for native speakers. Results are explained in terms of FO contours highlighting important content words. Intrinsic vowel pitch is also argued to contribute. Further study is required to determine why speech interferers caused listeners to rely more heavily on FO cues, and to investigate the influence of other prosodic cues on speech intelligibility.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:584160 |
| Date | January 2007 |
| Creators | Binns, Christine |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/55671/ |
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