Bilateral Cochlear Implants and Enhanced Spatial Cues
Brown (2014) reports that bilateral cochlear implant (BCI) users typically receive only limited binaural cues and “show little improvement to speech intelligibility from spatial cues….” Therefore, Brown artificially extended interaural loudness differences (ILDs, which normally occur above 1,500 Hz) into the low frequencies, where they would be better perceived by BCI users. He compared results from naturally occurring ILDs and artificially extended ILDs. Of note, to achieve artificially enhanced ILDs, he estimated instantaneous interaural timing differences (ITDs, which are greatest below 1,500 Hz) in the low frequency region and converted them to ILDs (which are not naturally present in the low frequency region).
Eight BCI patients participated using their own maps. The masker/talker was presented on one side of the head while the target/talker was presented on the other. The pattern of results indicated speech intelligibility can be improved via binaural cue enhancement. Brown reported that “binaural enhancement provided an additional 31 percentage points of speech intelligibility…” with regard to binaural cues typically available to BCI users. Indeed, each participant benefited from spatial cue enhancement and each participant “preferred listening to the enhanced stimuli…” as it was easier to attend to the person speaking.
Brown reports the study offers “proof of concept” that binaural enhancement of spatial cues may be of significant benefit for BCI users. Nonetheless, “synchronization between BCIs would be necessary for the current binaural enhancement algorithm to be implemented…” and although BCI synchronization is feasible, it is not currently available commercially.
For More Information, References, and Recommendations
Brown CA. (2014) Binaural Enhancement for Bilateral Cochlear Implant Users. Ear & Hearing 35 (5):580-584.