I am currently working on speech coding in cochlear implant patients with Dr Rob Morse at Aston. We are testing the strategy of adding noise to the speech signal as a way of improving speech reception. A nerve response in a normal-hearing listener includes a high degree of randomness, or stochasticity, in the timing of nerve impulses. Direct electrical stimulation of the nerve by the implant bypasses the major source of this stochasticity, the inner hair cells in the cochlea. By adding noise to the signal transmitted by the implant, this stochastic nerve activity can be reintroduced, which we believe will improve the information available to the patient.
I previously worked with Professor Brian Roberts, also at Aston, studying normal human auditory perception, particularly looking at auditory grouping; how the auditory system processes mixtures of sounds and extracts auditory objects. Our experiments looked at the use of harmonicity as a cue for the simultaneous grouping of components, and segregation of sounds by onset time difference (asynchrony).
I use both psychophysical and computer modelling techniques to investigate these issues. I am also interested pitch perception and auditory models of human and non-human hearing.
Research Fellow, Audiology, Aston University, 2007-
EPSRC project entitled “Enhanced cochlear implant coding using stochastic beam forming”. (With Dr Rob Morse)
Research Fellow, Psychology, Aston University, 2005-2007
Research Fellow, Psychology, University of Birmingham, 2003-2005. BBSRC project entitled “Brainstem mechanisms for the perceptual segregation and fusion of auditory objects”. (With Prof. Brian Roberts).
PhD (Psychology), University of Essex, 1999-2003. Thesis title: “Segregation of concurrent vowels: An auditory model” (With Prof Ray Meddis)
MSc (Cognitive Science), University of Manchester, 1998-9. Thesis title: “An information theoretic approach to auditory stream segregation” (With Dr Neil Todd)
BSc (Psychology), University of Leicester, 1990-1993
- Roberts, B., and Holmes, S.D. (2007). “Contralateral influences of wideband inhibition on the effect of onset asynchrony as a cue for auditory grouping.” Journal of the Acoustical Society of America, 121, pps tbc
- Roberts, B., and Holmes, S.D. (2006). “Grouping and the pitch of a mistuned fundamental component: Effects of applying simultaneous multiple mistunings to the other harmonics.” Hearing Research, 222, 79-88. Download manuscript
- Holmes, S.D., and Roberts, B. (2006). “Inhibitory influences on asynchrony as a cue for auditory segregation.” Journal of Experimental Psychology, Human Perception and Performance, 32, 1231-1242. Download manuscript
- Roberts, B., and Holmes, S.D. (2006). “Asynchrony and the grouping of vowel components: Captor tones revisited.” Journal of the Acoustical Society of America, 119, 2905-2918. Download pdf. (Journal Homepage)
- Holmes, S.D., Sumner, C.J., O’Mard, L.P., and Meddis, R. (2004). “The temporal representation of speech in a nonlinear model of the guinea pig cochlea.” Journal of the Acoustical Society of America, 116, 3534-3545. Download pdf. (Journal Homepage)
- Roberts, B., Holmes, S.D., Bleeck, S. and Winter, I.M. (In Press). “Wideband inhibition modulates the effect of onset asynchrony as a grouping cue,” Proceedings of the XIVth International Symposium on Hearing, Cloppenburg, Germany. [To appear in: Hearing – from basic research to applications, edited by B. Kollmeier, G. Klump, V. Hohmann, U. Langemann, M. Mauermann, S. Uppenkamp. and J. Verhey, Springer Verlag, expected spring 2007]. Download manuscript
Pdfs of full articles are available where permission is given by the journal. Where permission is not given a manuscipt is available which may contain some minor differences from the published article.