ORIGINAL STUDY Envelope Expansion of Sine Wave Vocoded Speech

Cochlear implants are an accepted and effective treatment for restoring hearing sensation to people with severe-to profound hearing loss. Contemporary cochlear implants consist of a microphone, a sound processor, a transmitter, a receiver, and an electrode array that is positioned inside the cochlea. The sound processor is responsible for decomposing the input audio signal into different frequency bands and delivering information about each frequency band to the appropriate electrode in a base-to-apex tonotopic pattern. The bandwidths of the frequency bands are approximately equal to the critical bands, where lowfrequency bands have higher frequency resolution than high-frequency bands. The actual stimulation to each electrode consists of nonoverlapping biphasic chargebalanced pulses that are modulated by the low passfiltered output of each analysis filter. However, the improvement in speech perception necessitates a highly sophisticated way of processing the speech and coding to the auditory nerve fibers.