Objective speech intelligibility measurement for cochlear implant users in complex listening environments

• Five objective speech intelligibility measures are assessed for cochlear implant users.
• A CI-inspired non-intrusive measure is proposed based on extending a previously-proposed measure.
• The modified measure uses an acoustic filterbank to emulate cochlear implant hearing percepts.
• Accurate results are obtained, with the advantage of not requiring a clean reference signal.
• A modulation filterbank ranging from 4 to 64 Hz is shown to better simulate cochlear implant hearing.

Objective intelligibility measurement allows for reliable, low-cost, and repeatable assessment of innovative speech processing technologies, thus dispensing costly and time-consuming subjective tests. To date, existing objective measures have focused on normal hearing model, and limited use has been found for restorative hearing instruments such as cochlear implants (CIs). In this paper, we have evaluated the performance of five existing objective measures, as well as proposed two refinements to one particular measure to better emulate CI hearing, under complex listening conditions involving noise-only, reverberation-only, and noise-plus-reverberation. Performance is assessed against subjectively rated data. Experimental results show that the proposed CI-inspired objective measures outperformed all existing measures; gains by as much as 22% could be achieved in rank correlation.