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International Journal of Otolaryngology
Volume 2012 (2012), Article ID 518202, 10 pages
http://dx.doi.org/10.1155/2012/518202
Research Article

Electroacoustic Comparison of Hearing Aid Output of Phonemes in Running Speech versus Isolation: Implications for Aided Cortical Auditory Evoked Potentials Testing

1Health and Rehabilitation Sciences (Hearing Sciences), National Centre for Audiology, Faculty of Health Sciences, Western University, London, ON, Canada N6G 1H1
2National Centre for Audiology and School of Communication Sciences and Disorders, Western University, London, ON, Canada N6G 1H1

Received 30 September 2012; Accepted 28 November 2012

Academic Editor: Catherine McMahon

Copyright © 2012 Vijayalakshmi Easwar et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background. Functioning of nonlinear hearing aids varies with characteristics of input stimuli. In the past decade, aided speech evoked cortical auditory evoked potentials (CAEPs) have been proposed for validation of hearing aid fittings. However, unlike in running speech, phonemes presented as stimuli during CAEP testing are preceded by silent intervals of over one second. Hence, the present study aimed to compare if hearing aids process phonemes similarly in running speech and in CAEP testing contexts. Method. A sample of ten hearing aids was used. Overall phoneme level and phoneme onset level of eight phonemes in both contexts were compared at three input levels representing conversational speech levels. Results. Differences of over 3 dB between the two contexts were noted in one-fourth of the observations measuring overall phoneme levels and in one-third of the observations measuring phoneme onset level. In a majority of these differences, output levels of phonemes were higher in the running speech context. These differences varied across hearing aids. Conclusion. Lower output levels in the isolation context may have implications for calibration and estimation of audibility based on CAEPs. The variability across hearing aids observed could make it challenging to predict differences on an individual basis.