Effect of hearing aid bandwidth on speech recognition performance of listeners using a cochlear implant and...

The purpose of this study was to determine how the bandwidth of the hearing aid (HA) fitting affects bimodal speech recognition of listeners with a cochlear implant (CI) in one ear and severe-to-profound hearing loss in the unimplanted ear (but with residual hearing sufficient for wideband amplification using National Acoustic Laboratories Revised, Profound [NAL-RP] prescriptive guidelines; unaided thresholds no poorer than 95 dB HL through 2000 Hz).

Recognition of sentence material in quiet and in noise was measured with the CI alone and with CI plus HA as the amplification provided by the HA in the high and mid-frequency regions was systematically reduced from the wideband condition (NAL-RP prescription). Modified bandwidths included upper frequency cutoffs of 2000, 1000, or 500 Hz.

On average, significant bimodal benefit was obtained when the HA provided amplification at all frequencies with aidable residual hearing. Limiting the HA bandwidth to only low-frequency amplification (below 1000 Hz) did not yield significant improvements in performance over listening with the CI alone.

These data suggest the importance of providing amplification across as wide a frequency region as permitted by audiometric thresholds in the HA used by bimodal users.