Noise reduction in cochlear implant speech processors

Journal/Book: Hno. 1995; 43: 175 Fifth Ave, New York, NY 10010. Springer Verlag. 545-551.

Abstract: Cochlear implant wearers suffer from all additional impairment of auditory-verbal communication due to environmental noise, similar to that experienced by many users of conventional hearing aids. To reduce this problem the mini-22 cochlear implant system has implemented a noise suppression function in the Mini Speech Processor (MSP) decreasing background noise-induced stimulation. The efficacy of this algorithm was investigated in IX experienced postlingually-deafened adult cochlear implant users. By means of a computer-assisted speech intelligibility measurement unit, speech understanding was compared with and without the noise suppression function. Paired observations were conducted in noise as well as in silence. The recording of complete performance-intensity functions in terms of speech discrimination tested with the standardized Freiburg speech intelligibility test and a newly developed sentence test demonstrated the benefit of the noise reduction mechanism. Better understanding was achieved in silence in the normal speech processing mode of the MSP, whereas a significant improvement in noise resulted from the noise suppression. Considerable interindividual differences were found in the gain patients derived from using the noise suppression algorithm. The more often the S-position was used, the better the individual result with activated noise suppression. However, providing the cochlear implant patients with more information, as in the spectral peak (''SPEAK'') stimulation strategy recently developed by Cochlear Corporation, could lead to higher speech discrimination scores in interfering noise. Paired comparison studies revealed that the new strategy added significantly to results of speech understanding. Average intelligibility rose 40% when using the new coding method instead of the MSP with activated noise suppression. The noise suppression function in the SPEAK does not seem to have a significant effect in either noise or silence.

Note: Article J Mullerdeile, Christian Albrechts Univ Kiel, Hno Heilkunde Kopf & Halschirurg Klin, Arnold Heller Str 14, D-24105 Kiel, Germany

Keyword(s): cochlear implant; speech audiometry; noise; sentence test

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