Non-negative matrix factorization on the envelope matrix in cochlear implant

Cochlear implants (CIs) require efficient speech processing to maximize information transfer to the brain, especially in noise. Since speech information in CI is coded in the waveform envelope which is non-negative and is highly correlated to firing of auditory neurons, a novel CI processing strategy is proposed in which sparse constraint non-negative matrix factorization (NMF) is applied to the envelope matrix of 22 frequency channels in order to improve the CI performance in noisy environments. The proposed strategy is evaluated by subjective speech reception threshold (SRT) experiments and subjective quality rating tests at three SNRs. Compared to the default commercially available CI processing strategy, the advanced combination encoder (ACE), the NMF algorithm significantly enhanced speech intelligibility and improved speech quality in the 0 dB and 5 dB for normal hearing subjects with vocoded speech, but not in the 10 dB.