Effects of noise and noise reduction processing on the operation of the Nucleus-22 cochlear implant processor.

Cochlear implants, like other types of auditory sensory aids, become increasingly ineffective with increasing ambient noise levels . One method of signal processing to reduce additive random wideband noise, the INTEL method, has been used to good effect as an input preprocessor for the Nucleus-22 cochlear implant . The implant 's own signal processor estimates and encodes pitch frequency and the frequencies of Formants 1 and 2. The study reported here shows that additive noise results in substantial deviations in formant frequency estimates from those that would be observed in the absence of noise . When noisy speech is preprocessed by the INTEL method to reduce noise intensity, the deviations in the frequency estimates for Formant 2 are substantially reduced.