EFFECTS OF INTERRUPTING NOISE AND SPEECH REPAIR MECHANISMS IN ADULT COCHLEAR-IMPLANT USERS

Abstract

The long-term objective of this project is to help cochlear-implant (CI) users achieve better speech understanding in noisy, real-world listening environments. The specific objective of the proposed research is to evaluate why speech repair (“restoration”) mechanisms are often atypical or absent in this population. Restoration allows for improved speech understanding when signals are interrupted with noise, at least among normal-hearing listeners. These experiments measured how CI device factors like noise-reduction algorithms and compression and listener factors like peripheral auditory encoding and linguistic skills affected restoration mechanisms. We hypothesized that device factors reduce opportunities to restore speech; noise in the restoration paradigm must act as a plausible masker in order to prompt the illusion of intact speech, and CIs are designed to attenuate noise. We also hypothesized that CI users, when listening with an ear with better peripheral auditory encoding and provided with a semantic cue, would show improved restoration ability. The interaction of high-quality bottom-up acoustic information with top-down linguistic knowledge is integral to the restoration paradigm, and thus restoration could be possible if CI users listen to noise-interrupted speech with a “better ear” and have opportunities to utilize their linguistic knowledge. We found that CI users generally failed to restore speech regardless of device factors, ear presentation, and semantic cue availability. For CI users, interrupting noise apparently serves as an interferer rather than a promoter of restoration. The most common concern among CI users is difficulty understanding speech in noisy listening conditions; our results indicate that one reason for this difficulty could be that CI users are unable to utilize tools like restoration to process noise-interrupted speech effectively.