Evaluation of the Low Power Speech Coding Strategy MP3000™

Introduction:

The aim of the presented study was to evaluate whether battery life savings can be achieved by a reduction of stimulation rate of the MP3000™ speech coding strategy without compromising the speech intelligibility of the cochlear implant patients.

Methods:

A take home trial providing two weeks of accommodation for the following four conditions was conducted: ACE 8 maxima with 900 pps, MP3000 6 maxima with 720 pps, MP3000 5 maxima with 720 pps and MP3000 5 maxima with 500 pps. Fourteen subjects using a Hybrid-L cochlea implant with acoustic component were tested for speech intelligibility. To investigate the effect of the T-Level setting on speech understanding, 8 subjects with electrical stimulation only were tested with identical T-levels well as with slightly elevated T-levels.

Results:

An extension of the average battery life by 41%, 32% and 20% was measured in the conditions with 5 maxima 500 pps, 5 maxima 720 pps and 6 maxima 720 pps, respectively. Subjects showed no difference between ACE and MP3000 for speech perception at normal conversation levels (65 dB SPL). The performance at soft stimulation levels (50 dB SPL) was related to the changes of T-levels between ACE and MP3000. Identical T-levels resulted in significantly decreased speech intelligibility of MP3000™ 5 maxima, 720 pps at 50 dB SPL and increased T-levels recovered the speech intelligibility to the ACE control condition.

Discussion:

The presented results show no significant speech intelligibility difference and longer battery life with the MP3000 speech coding strategy for cochlear implant patients. Beside adjustment of the C-level profile, MP3000 fitting should also include T-levels adaptation in order to preserve speech intelligibility at soft levels.