Influence of a single reflection on speech intelligibility in simulated electric‐acoustic stimulation.

Abstract

In reverberant environments, reflections occurring within 30–50 ms of the direct speech assist intelligibility by perceptually fusing with the source, effectively increasing its level. Fusion occurs at similar delays in monaurally deaf and normal‐hearing listeners, suggesting an independence from binaural processes [Litovsky et al., J. Acoust. Soc. Am. 106, 1633–1654 (1999)]. Its effects can thus be examined in unilateral cochlear implant (CI) users. Simulated CI listening shows little benefit from early reflections, and a detriment when delays exceed 20 ms [Whitmal and Poissant, Conference on Implantable Auditory Prostheses (2009)]. Data from our laboratory show that CI users with residual acoustic hearing benefit from electric‐acoustic stimulation (EAS) in reverberation. The role of early reflections in this EAS benefit remains unclear. The present study examined the effect of a single unattenuated reflection at ten delay times on intelligibility in simulated EAS. Target stimuli consisted of sentences combined with unattenuated copies delayed by 0–66 ms. Four‐talker babble was added to increase difficulty. A four‐channel vocoder simulated electric stimulation; low‐pass filtered speech represented residual acoustic hearing. Monaural intelligibility scores from normal‐hearing listeners under anechoic and reflected conditions with electric and electric‐acoustic processing suggest that EAS may facilitate a benefit from early reflections. [Work supported by the NIDCD.]