The effect of auditory feedback alterations on the speech quality of hearing aid and cochlear implant users

Abstract

The speech of seven hearing aid (HA) users with severe-profound hearing loss and six cochlear implant (CI) users was recorded as they read the Rainbow Passage while their speech feedback was either spectrally altered in real-time, completely masked by multi-talker babble noise, or unaltered. Spectral alterations were implemented by filtering the speech signal into either one or four frequency bands, extracting their respective amplitude envelope(s), and amplitude-modulating the corresponding noise band(s). While the single-band condition provided only coarse information about the speech rhythmic structure, the four-band noise signal remained intelligible. Auditory feedback was presented via insert earphones to the HA users, and via the auxiliary jack (with the headpiece microphone silenced) to the CI users, at the participants’ most comfortable listening level. The quality of the recorded speech (separated into individual sentences) was assessed using a 2IFC procedure. For each combination of the experimental conditions, six judges selected the more natural-sounding utterance in a pair. Preference scores were calculated for each of the four feedback conditions and statistically tested. HA and CI group differed in how feedback intelligibility affected the speech quality. Possible acoustic correlates of the perceived differences will be discussed.