[On the effect of reverberation on speech intelligibility by cochlear implant listeners]

An important parameter for characterization of the acoustic quality of closed rooms is reverberation. There is a rising interest in evaluating the ability of cochlear implant (CI) users to understand speech in real-world environments. Whereas the influence of noise on speech perception has been widely investigated, much less is known about the detrimental effect of reverberation. The present study aimed to investigate the influence of reverberation time on the speech perception of CI users and subjects with normal hearing.

A reverberated version of the sentences of the Oldenburg sentence test (OLSA) which is a widely used German test to measure speech reception thresholds (SRT) in cochlear implant users was generated using professional audio processing software. The reverberation times used were 0.7, 1.0, 1.5 and 2.0 s. For these four reverberation times and for a non-reverberated control condition, the SRT was measured in eight adult CI users and in eight subjects with normal hearing.

To characterize the detrimental effect of reverberation the SRT differences between the reverberated and non-reverberated conditions were calculated. These SRT differences revealed a significant effect of reverberation in CI users with, e.g. a mean SRT increase of 2.9 dB in CI users and 0.9 dB in subjects with normal hearing for a reverberation time of 0.7 s. A strong correlation was found between the SRT increase and the SRT in the non-reverberated condition, highlighting the problems of poor performers in reverberant environments.

The results of the current investigation indicated that reverberation results in decreased speech understanding of CI users.