A novel acoustic simulation of cochlear implant hearing: effects of temporal fine structure

Acoustic simulations of cochlear implant signal processing have been widely used to determine the upper bounds on speech perception using these devices. These simulations assume that the only temporal information delivered to the inner ear is the envelope of the signal and that spectral cues, determined by the number of channels present, are the primary determinant of speech perception ability. While highly informative, such simulations fail to explain open-set speech perception obtained by some patients who received single channel implants as young children. In addition, some implant recipients enjoy and appreciate music to an extent not possible if envelope is the sole source of temporal information. A novel acoustic simulation algorithm is described which allows varying the degree to which temporal fine structure is delivered to the cochlea. Use of this algorithm demonstrates that while high levels of speech perception in quiet can be provided with only six channels of envelope, inclusion of even small amounts of temporal fine structure dramatically improves perception of speech in noise, timbre and melody.