The Enhancement of Onsets in the Speech Envelope increases Speech Intelligibility in Noise Vocoded Cochlear Implant Simulations

peech understanding with cochlear implants (CIs) can be good in quiet, but very poor in more adverse listening conditions. One objective of speech enhancement algorithms is to improve the intelligibility of noisy speech signals. Recent studies showed that the transient parts of a speech signal contribute most to speech intelligibility in normal-hearing (NH) listeners. In this study, the influence of onset envelope enhancement on speech intelligibility in noisy conditions using an eight channel cochlear implant signal processor vocoder was investigated. Sentences and consonant-vowel-consonant (CVC) words were processed with modified versions of the enhanced envelope continuous interleaved sampling (EECIS) and the transient emphasis spectral maxima (TESM) CI strategies relative to the standard CIS reference. Both strategies emphasize speech elements containing much phonetic information by deriving an additional gain at transient parts of the signal in each frequency band. The signals were presented in speech-shaped noise (SSN) to NH listeners at signal-to-noise ratios (SNRs) of 4 to -4 dB for sentences and at 12, 6 and 0 dB for CVC words. The sentence recognition task showed a significant speech reception threshold (SRT) improvement of 2.5 dB for the EECIS and 1.5 dB for the TESM strategy. The difference in SRT between the two envelope enhancement strategies was also significant. In the CVC word test, significant effects between the EECIS and the CIS strategies were obtained for the initial and final consonant recognition. An information transmission analysis of the results showed that the transmission of the consonant features place, manner and voicing was improved. The presented results indicate that the enhancement of onsets in the speech envelope can improve speech intelligibility for vocoded speech in noisy environments due to a better perception of the transient cues of the speech signal.status: publishe