Loudness functions for patients with functional hearing loss

Abstract

Objectives

To compare the loudness functions (loudness ratings as a function of sound level) obtained from patients diagnosed as having functional hearing loss (FHL) with those for patients with sensorineural hearing loss (SNHL) and healthy volunteers.

Design

Loudness functions for a 1000 Hz tone for patients with FHL and SNHL were assessed based on the categorical loudness scaling method. The data were compared with control data obtained in our facilities.

Study sample

18 patients (33 ears) with FHL and 10 patients (19 ears) with SNHL.

Results

For patients with SNHL and healthy volunteers, loudness increased progressively with increasing sound level above the audiometric threshold, with no exceptions. However, for about 70% of the patients with FHL, a different type of loudness function was obtained; the thresholds determined from the loudness function, which were defined as the minimum sound levels at which loudness could be judged, were 10 dB or more lower than the audiometric threshold (>10 dB), and/or the loudness ratings were elevated for a sound at the audiometric threshold.

Conclusions

The results support the hypothesis that patients with FHL often make threshold judgments based on a certain loudness.

Keywords:

• Functional hearing loss
• pseudohypacusis
• loudness function
• Békésy audiometry
• categorical loudness scaling

Acknowledgements

The authors sincerely thank the reviewers for their helpful suggestions and comments, which have helped us to improve the paper substantially.

Disclosure statement

The authors have no conflicts of interest to disclose.

Additional information

Funding

This study was financially supported by a grant-in-aid from the Ministry of Education, Culture, Sports, Science and Technology of Japan for fiscal 2019–2020.