The effect of reflections, reverberation, and echoes on speech recognition by hearing-impaired adults
This project is no longer available.
PhD in Experimental Psychology
with Dr Michael A Akeroyd (MRC-IHR) and Professor Pascal Belin (University of Glasgow)
maa@ihr.gla.ac.uk, p.belin@psy.gla.ac.uk
The three-dimensional auditory world is acoustically far more complex than it is perceived to be. Every object or surface in a room reflects sound to some extent, but the auditory system usually suppresses these reflections so that they are not noticed separately. Yet these reflections seem to add to speech intelligibility. This project will investigate this dissociation, concentrating on the effects on older hearing-impaired adults and what hearing aids do.
Many architectural experiments have demonstrated that reflections arriving within about 80-100 ms of the first-arriving, direct sound add to speech intelligibility. But the location of the sound is determined without any of these interfering (the .precedence effect.): all reflections arriving within 20 ms are perceptually minimised and reflections arriving later are perceived as separate sounds The latest data in this area (Arweiler and Buchholz, 2011) from hearing-impaired listeners indicated, surprisingly, that they did not show any deficits compared to normal-hearing listeners. We will extend these experiments to further understand how hearing-impaired listeners identify speech in reverberant environments. These experiments will use the loudspeaker ring at the IHR Scottish Section, which can reproduce complex acoustical environments and simulate distant sound sources (e.g. Akeroyd et al, 2007). We will also test the hypothesis that the speech-intelligibility vs location dissociation is related to the .what. vs. .where. theory in auditory neuroscience (eg Alain et al. 2001), for which we will use human functional magnetic resonance imaging (fMRI) at the Center for Cognitive Neuroimaging in Glasgow University.
Applications are welcome from graduates with a first- or upper second-class degree in a relevant discipline, such as psychology or cognitive neuroscience. An interest in hearing, speech, or hearing impairment is advantageous, although full training will be given. If appropriate there will be the opportunity to begin with the one-year taught Masters (MRes) at the University of Glasgow on Research Methods of Psychological Science. IHR will provide full financial support for both the MRes and PhD.
Akeroyd MA, Gatehouse S, Blaschke J (2007) The detection of differences in the cues to distance by elderly hearing-impaired listeners. J. Acoust. Soc. Am. 121:1077-1089.
Alain C, Arnott SR, Hevenor S, Graham S, Grady, CL (2001). "What" and "where" in the human auditory system. Proc Natl Acad Sci USA 98:12301-1306
Arweiler I, Buchholz JM (2011) The influence of spectral characteristics of early reflections on speech intelligibility. J. Acoust. Soc. Am. 130:996-1005.