Exploration of a physiologically-inspired hearing-aid algorithm using a computer model mimicking impaired hearing

Abstract

Objective: To use a computer model of impaired hearing to explore the effects of a physiologically-inspired hearing-aid algorithm on a range of psychoacoustic measures. Design: A computer model of a hypothetical impaired listener’s hearing was constructed by adjusting parameters of a computer model of normal hearing. Absolute thresholds, estimates of compression, and frequency selectivity (summarized to a hearing profile) were assessed using this model with and without pre-processing the stimuli by a hearing-aid algorithm. The influence of different settings of the algorithm on the impaired profile was investigated. To validate the model predictions, the effect of the algorithm on hearing profiles of human impaired listeners was measured. Study sample: A computer model simulating impaired hearing (total absence of basilar membrane compression) was used, and three hearing-impaired listeners participated. Results: The hearing profiles of the model and the listeners showed substantial changes when the test stimuli were pre-processed by the hearing-aid algorithm. These changes consisted of lower absolute thresholds, steeper temporal masking curves, and sharper psychophysical tuning curves. Conclusion: The hearing-aid algorithm affected the impaired hearing profile of the model to approximate a normal hearing profile. Qualitatively similar results were found with the impaired listeners’ hearing profiles.

Key Words:

• Auditory model
• algorithm evaluation
• normal and impaired hearing
• psychoacoustics

Acknowledgements

This work was supported by the DFG Cluster of Excellence EXC 1077/1 “Hearing4all”. Special thanks to Christopher J. Plack for fruitful discussion and Gitte Keidser, Enrique A. Lopez-Poveda, and two anonymous reviewers, who greatly helped to improve the manuscript.

Declaration of interest

The authors report no declaration of interest.

Notes

Notes

1. www.bioaid.org.uk, last visited 25 November 2015.

2. No hard level limiter was used in the current hearing-aid algorithm implementation. A level limit was given by the psychoacoustic procedures (103 dB SPL).

3. Interestingly, the right-hand tail of an IFMC, which shows already high masker levels even when introducing gain and compression only (Figure 3, D), is not changed much under the additional influence of the MOC-processing. This is due to the fact that the masker level here is already above the compression threshold. Above the compression threshold even a substantial attenuation due to the MOC-processing of the input level is mapped only to a small (compressed) attenuation of the output level. This effect ‘neutralizes’ the effect of the MOC-processing on the right-hand tail of an IFMC.

4. The absolute threshold at 8 kHz was not restored for IH67 due to insufficient gain in the 8 kHz hearing-aid algorithm channel (which was requested by this listener).

5. Lopez-Poveda and Meddis (2001) already anticipated that the DRNL model could be used to design or test hearing-aid algorithms.