[Noise signal reduction in cochlear implant speech processors].

Cochlear implant wearers suffer from an 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 18 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.(ABSTRACT TRUNCATED AT 250 WORDS)