Effect of bandwidth extension to telephone speech recognition in cochlear implant users.

The present study investigated a bandwidth extension method to enhance telephone speech understanding for cochlear implant (CI) users. The acoustic information above telephone speech transmission range (i.e., 3400 Hz) was estimated based on trained models describing the relation between narrow-band and wide-band speech. The effect of the bandwidth extension method was evaluated with IEEE sentence recognition tests in seven CI users. Results showed a relatively modest but significant improvement in the speech recognition with the proposed method. The effect of bandwidth extension method was also observed to be highly dependent on individual CI users.