Enhancing the speech envelope of continuous interleaved sampling processors for cochlear implants

A new method to code the speech envelope in continuous interleaved sampling (CIS) processors for cochlear implants is proposed. In this enhanced envel ope, the rapid adaptation seen in the response of auditory nerves to sound stimuli is incorporated. Two strategies, one using the standard envelope (C IS) and one using the enhanced envelope (EECIS), were tested perceptually w ith six postlingually deafened users of the LAURA cochlear implant. The tes ts included identification of stop consonants in three different vowel cont exts and monosyllabic consonant-vowel-consonant (CVC) words. Significant im provements in correct identification scores were observed fur stop consonan ts in intervocalic /a/ context (p = 0.026): average results varied from 46% correct for CIS to 55% for EECIS. This improvement was mainly due to the b etter transmission of place of articulation. The differences in identificat ion scores for stop consonants in /i/ and /u/ context were not significant. The identification scores for the medial vowels of the CVC words were sign ificantly higher when the EECIS strategy was used: average results increase d from 39% correct to 46% correct (p = 0.018). No significant differences w ere observed between the results for initial and final consonants of the CV C words. The present results demonstrate that the inclusion of the rapid ad aptation in the speech processing for cochlear implants can improve speech intelligibility. (C) 1999 Acoustical Society of America. [S0001-4966(99)027 04-6].