Categorical loudness scaling in cochlear implant recipients

Abstract

Objective: This study investigated categorical loudness scaling in a large group of cochlear implant (CI) recipients. Design: Categorical loudness was measured for individually determined sets of current amplitudes on apical, mid and basal electrodes of the Nucleus array. Study sample: Thirty adult subjects implanted with the Nucleus CI. Results: Subjects were generally reliable in categorical loudness scaling. As expected, current levels eliciting the same loudness categories differed across subjects and electrodes in many cases. After scaling the electric levels to remove differences in dynamic ranges across subjects and electrodes, the across-subject loudness functions for the three electrodes were very similar. Conclusions: Scaled electric current to remove differences in dynamic range, as implemented in the Nucleus processor, ensures uniform loudness across the array and CI recipients. The results also showed that categorical loudness scaling for electric stimulation was similar to that for acoustic stimulation in normal hearing subjects. These findings could be used as a guide for aligning electric and acoustic loudness in CI recipients with contralateral hearing.

Key Words:

• Cochlear implant
• psychoacoustics/hearing science
• behavioural measures
• assistive technology

Acknowledgements

This research was supported by Cochlear Limited and the HEARing CRC, established and supported under the Cooperative Research Centres Program – an Australian Government Initiative. We wish to thank Kieran Reed for software development, the 30 CI subjects for their participation, Dr. Wiebke Heeren for the results from her study, and the reviewers for their helpful comments.

Declaration of interest

The first author is employed by Cochlear Limited.