Utilizing different channels for multiple inputs in cochlear implant processing

Abstract

While cochlear implants successfully provide auditory sensation for deaf people, speech understanding through the device is compromised when there is a background noise or competing sounds, partly due to implant users’ reduced ability in auditory grouping. The present study investigates whether providing multiple streams of input on different channels would facilitate auditory grouping, thereby assisting speech understanding in competing sounds. In acoustic hearing, presenting two streams of input (such as speech and noise) in spectrally separate channels gener- ally facilitates grouping; however, in electric hearing it is difficult to predict and separating them could lead to a negative result, because channel interactions inferred from the excitation patterns are severe and the actual amount of electric current for the noise delivered to the cochlea would be much higher for a given SNR, therefore contaminating the target more effectively. Results from consonant identification measured in a variety of speech/noise conditions (same/different channels) indicate that speech understanding generally improves with separate channels, implying that implant users appear to extract speech information on the basis of spatial (channel) separation, easily overcoming the distracter from the adjacent channels with higher intensity. This also proposes a new measure of channel interactions based on auditory grouping.