Single sideband encoder for music coding in cochlear implants

The restoration of melody perception is a key remaining challenge in cochlear implants. We propose a new sound coding strategy that converts an audio signal into time-varying electrically stimulating pulse trains. A sound is first split into several frequency subbands and each subband signal is coherently downward shifted to a low-frequency base band, similar to demodulation used in single sideband (SSB) radios. These resulting coherent envelope signals have Hermitian symmetric frequency spectrums and are thus real-valued. A peak detector in each subband further converts the coherent envelopes into rate-varying and interleaved pulse trains. Acoustic simulations of cochlear implants with normal hearing listeners showed significant improvement in melody recognition over the most common stimulation approach used in cochlear implants.