A model for predicting localization performance in cochlear implant users

Douglas A. Miller, Mohammad A. Matin

Department of Electrical and Computer Engineering, Daniel Felix Ritchie School of Engineering and Computer Science, University of Denver, Denver, USA.

DOI: 10.4236/wjns.2013.33017                

Abstract

Mathematical models can be very useful for understanding complicated systems, and for testing algorithms through simulation that would be difficult or expensive to implement. This paper describes the proposal for a model that would simulate the sound localization performance of profoundly hearing-impaired persons using bilateral cochlear implants (CIs). The expectation is that this model could be used as a tool that could prove useful in developing new signal processing algorithms for neural encoding strategies. The head related transfer function (HRTF) is a critical component of this model, and provides the base characteristics of head shadow, torso and pinna effects. This defines the temporal, intensity and spectral cues that are important to sound localization. This model was first developed to simulate normal hearing persons and validated against published literature on HRTFs and localization. The model was then further developed to account for the differences in the signal pathway of the CI user due to sound processing effects, and the microphone location versus ear canal acoustics. Finally, the localization error calculated from the model for CI users was compared to published localization data obtained from this population.

Keywords

Head Related Transfer Function; HRTF; Localization; Cochlear Implant

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Durlach, N.I. and Colburn, H.S. (1978) Binaural phenomena. In: Carterette, E.C. and Friedman, M.P., Eds., Handbook of Perception, Vol. 4, Academic, New York.
[2]	Bronkhurst, A.W. and Plomp, R. (1988) The effect of head-induced interaural time and level differences on speech intelligibility in noise. Journal of the Acoustical Society of America, 86, 1374-1383.
[3]	Zurek, P. (1993) Binaural advantages and direction effects in speech intelligibility. In: Studebaker, G.A. and Hochberg, I., Eds., Acoustical Factors Affecting Hearing Aid Performance, 2nd Edition, Allyn & Bacon, Boston, 255-276.
[4]	Shaw, E.A. (1974) Transformation of sound pressure level from the free field to the eardrum in the horizontal plane. Journal of the Acoustical Society of America, 56, 1848-1861. doi:10.1121/1.1903522
[5]	Yost, W. and Dye. R. (1997) Fundamentals of directional hearing. Semin Hear, 18, 321-344. doi:10.1055/s-0028-1083035
[6]	Miller, D.A. and Matin, M.A. (2011) Modeling the head related transfer function for sound localization in normal hearing persons and bilateral cochlear implant recipients. Proceedings of 14th International Conference on Computer and Information Technology (ICCIT 2011), San Diego, 22-24 December 2011, 344-349.
[7]	Brown, C.P. and Duda, R.O. (1998) A structural model for binaural sound synthesis. IEEE Transactions on Speech and Audio Processing, 6, 476-488. doi:10.1109/89.709673
[8]	Verschuur, C.A., Lutman, M.E., Ramsden, R., Greehan, P. and O’Driscoll, M. (2005) Auditory localization abilities in bilateral cochlear implant recipients. Otology & Neurotology, 26, 965-971. doi:10.1097/01.mao.0000185073.81070.07
[9]	van Hoesel, R.J.M. and Tyler, R.S. (2003) Speech perception, localization, and lateralization with bilateralcochlear implants. Journal of the Acoustical Society of America, 113, 1617-1630. doi:10.1121/1.1539520