Speech recognition in noise for cochlear implantees with a two-microphone monaural adaptive noise reduction system

Objective. In this study the performance of a noise reduction strategy appl ied to cochlear implants is evaluated. The noise reduction strategy is base d on a 2-channel adaptive filtering strategy using two microphones in a sin gle behind-the-ear hearing aid. Design: Four adult LAURA cochlear implant users (Peeters et al., 1993) took part in the experiments. The tests included identification of monosyllabic CVC (consonant-vowel-consonant) words and measurements of the speech recep tion threshold (SRT) of lists of numbers, in background noise presented at 90 degrees relative to the 0 degrees frontal direction of the speech. Perce nt correct phoneme scores for the CVC words at signal to noise ratios (SNRs ) of -5, 0, and +5 dB in steady speech-weighted noise at 60 dB SPL and SRTs for numbers in speech-weighted steady and nonsteady ICRA noise were both o btained in conditions with and without the noise reduction pre-processing. Physical SNR improvements of the noise reduction system are evaluated as we ll, as a function of the direction of the noise source. Results: Highly significant improvements in speech understanding, correspon ding on average to an SNR improvement of about 10 dB, were observed with th is 2-channel adaptive filtering noise reduction strategy using both types o f speech-noise test materials. These perceptual evaluations agree with phys ical evaluations and simulations of this noise reduction strategy. Taken to gether, these data demonstrate that cochlear implantees may increase their speech intelligibility in noisy environments with the use of multimicrophon e noise reduction systems.