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The Effects of Acoustic Bandwidth on Simulated Bimodal Benefit in Children and Adults with Normal Hearing

Sheffield, Sterling W.; Simha, Michelle; Jahn, Kelly N.; Gifford, René H.

doi: 10.1097/AUD.0000000000000281
Research Articles

Objectives: The primary purpose of this study was to examine the effect of acoustic bandwidth on bimodal benefit for speech recognition in normal-hearing children with a cochlear implant (CI) simulation in one ear and low-pass filtered stimuli in the contralateral ear. The effect of acoustic bandwidth on bimodal benefit in children was compared with the pattern of adults with normal hearing. Our hypothesis was that children would require a wider acoustic bandwidth than adults to (1) derive bimodal benefit, and (2) obtain asymptotic bimodal benefit.

Design: Nineteen children (6 to 12 years) and 10 adults with normal hearing participated in the study. Speech recognition was assessed via recorded sentences presented in a 20-talker babble. The AzBio female-talker sentences were used for the adults and the pediatric AzBio sentences (BabyBio) were used for the children. A CI simulation was presented to the right ear and low-pass filtered stimuli were presented to the left ear with the following cutoff frequencies: 250, 500, 750, 1000, and 1500 Hz.

Results: The primary findings were (1) adults achieved higher performance than children when presented with only low-pass filtered acoustic stimuli, (2) adults and children performed similarly in all the simulated CI and bimodal conditions, (3) children gained significant bimodal benefit with the addition of low-pass filtered speech at 250 Hz, and (4) unlike previous studies completed with adult bimodal patients, adults and children with normal hearing gained additional significant bimodal benefit with cutoff frequencies up to 1500 Hz with most of the additional benefit gained with energy below 750 Hz.

Conclusions: Acoustic bandwidth effects on simulated bimodal benefit were similar in children and adults with normal hearing. Should the current results generalize to children with CIs, these results suggest pediatric CI recipients may derive significant benefit from minimal acoustic hearing (<250 Hz) in the nonimplanted ear and increasing benefit with broader bandwidth. Knowledge of the effect of acoustic bandwidth on bimodal benefit in children may help direct clinical decisions regarding a second CI, continued bimodal hearing, and even optimizing acoustic amplification for the nonimplanted ear.

Previous studies examining the acoustic bandwidth required for bimodal benefit have been conducted with adult listeners. Pediatric data may provide information aiding clinical decision making regarding bimodal or bilateral candidacy. We sought to determine the effect of acoustic bandwidth on bimodal benefit in children and whether the pattern of benefit differed from adults with normal hearing and CIs. Results demonstrated that acoustic bandwidth effects on simulated bimodal benefit were similar in children and adults with normal hearing. Thus pediatric CI recipients may derive significant benefit from minimal acoustic hearing (<250 Hz) in the non-implanted ear and increasing benefit with broader bandwidth.

1Department of Hearing and Speech Sciences, Cochlear Implant Research Laboratory, Vanderbilt University, Nashville, Tennessee, USA; and 2Department of Communication Sciences and Disorders, University of South Florida, Tampa, Florida, USA.

This research was supported by Grants R01 DC009404 and R01 DC13117 from the NIDCD.

Portions of these data were presented at the 14th Symposium on Cochlear Implants in Children in December 2014 in Nashville, TN.

The authors have no conflicts of interest to disclose.

Received May 16, 2015; accepted January 4, 2016.

Address for correspondence: René H. Gifford, Department of Hearing and Speech Sciences, Cochlear Implant Research Laboratory, Vanderbilt University, 1215 21st Avenue South, MCE South, Room 8310, Nashville, TN 37232, USA. E-mail: rene.gifford@Vanderbilt.edu

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