Speech onset enhancement improves intelligibility in adverse listening conditions for cochlear implant users

Speech perception by cochlear implant (CI) users can be very good in quiet but their speech intelligibility (SI) performance decreases in noisy environments. Because recent studies have shown that transient parts of the speech envelope are most important for SI in normal-hearing (NH) listeners, the enhanced envelope (EE) strategy was developed to emphasize onset cues of the speech envelope in the CI signal processing chain. The influence of enhancement of the onsets of the speech envelope on SI was investigated with CI users for speech in stationary speech-shaped noise (SSN) and with an interfering talker. All CI users showed an immediate benefit when a priori knowledge was used for the onset enhancement. A SI improvement was obtained at signal-to-noise ratios (SNRs) below 6 dB, corresponding to a speech reception threshold (SRT) improvement of 2.1 dB. Furthermore, stop consonant reception was improved with the EE strategy in quiet and in SSN at 6 dB SNR. For speech in speech, the SRT improvements were 2.1 dB and 1 dB when the onsets of the target speaker with a priori knowledge of the signal components or of the mixture of the target and the interfering speaker were enhanced, respectively. The latter demonstrates that a small benefit can be obtained without a priori knowledge.