Spatial speech-in-noise performance in simulated single-sided deaf and bimodal cochlear implant users in comparison with real patients

Abstract

Objective

Speech reception thresholds (SRTs) in spatial scenarios were measured in simulated cochlear implant (CI) listeners with either contralateral normal hearing, or aided hearing impairment (bimodal), and compared to SRTs of real patients, who were measured using the exact same paradigm, to assess goodness of simulation.

Design

CI listening was simulated using a vocoder incorporating actual CI signal processing and physiologic details of electric stimulation on one side. Unprocessed signals or simulation of aided moderate or profound hearing impairment was used contralaterally. Three spatial speech-in-noise scenarios were tested using virtual acoustics to assess spatial release from masking (SRM) and combined benefit.

Study sample

Eleven normal-hearing listeners participated in the experiment.

Results

For contralateral normal and aided moderately impaired hearing, bilaterally assessed SRTs were not statistically different from unilateral SRTs of the better ear, indicating “better-ear-listening”. Combined benefit was only found for contralateral profound impaired hearing. As in patients, SRM was highest for contralateral normal hearing and decreased systematically with more severe simulated impairment. Comparison to actual patients showed good reproduction of SRTs, SRM, and better-ear-listening.

Conclusions

The simulations reproduced better-ear-listening as in patients and suggest that combined benefit in spatial scenes predominantly occurs when both ears show poor speech-in-noise performance.

Keywords:

• Cochlear implant
• vocoder
• speech intelligibility
• bimodal
• hearing aid
• virtual acoustics

Acknowledgements

The authors would like to thank all participants of the study, as well as K. Jonas Brännström and two anonymous reviewers for their constructive feedback on the manuscript. Special thanks also to Sven Kliesch and Nils Schreiber for conducting the experiments. Special thanks also to Brian C. J. Moore for detailed comments about the hearing impairment simulation.

Declaration of interest

TW reports grants from Advanced Bionics, grants from MED-EL, grants from Phonak Communications, outside the submitted work; and compensation for travel expenses from Advanced Bionics, Cochlear, MED-EL, Oticon Medical, and Phonak Communications. BW reports funding from United Kingdom Medical Research Council (MR/S002537/1) during revision of the manuscript.

This study was financed by DFG JU2858/2-1.

Data availability statement

Data is available from the corresponding author upon request. Code for the CI simulation can be found on https://doi.org/10.5281/zenodo.3234499, code for the hearing aid simulation can be found on http://www.openmha.org/