Output signal-to-noise ratio and speech perception in noise: effects of algorithm

Abstract

Objective: The aims of this study were to: 1) quantify the amount of change in signal-to-noise ratio (SNR) as a result of compression and noise reduction (NR) processing in devices from three hearing aid (HA) manufacturers and 2) use the SNR changes to predict changes in speech perception. We hypothesised that the SNR change would differ across processing type and manufacturer, and that improvements in SNR would relate to improvements in performance. Design: SNR at the output of the HAs was quantified using a phase-inversion technique. A linear mixed model was used to determine whether changes in SNR across HA conditions were predictive of changes in aided speech perception in noise. Study sample: Two groups participated: 25 participants had normal-hearing and 25 participants had mild to moderately severe sensorineural hearing loss. Results: The HAs programmed for both groups changed the SNR by a small, but statistically significant amount. Significant interactions in SNR changes were observed between HA devices and processing types. However, the change in SNR was not predictive of changes in speech perception. Conclusion: Although observed significant changes in SNR resulting from compression and NR did not convert to changes in speech perception, these algorithms may serve other purposes.

Key Words:

• Hearing aids
• speech perception
• behavioural measures
• noise
• assistive technology

Acknowledgements

All authors contributed to this work. C.M. designed and performed the experiment, analysed the data and wrote the manuscript as part of her dissertation work at the University of Washington. K.T., R.B. and Y.W. reviewed the design, data and analysis. J.L. helped with design and wrote the analysis MATLAB code and reviewed the manuscript. All authors discussed the results and implications, and commented on the manuscript at various stages. The authors thank Jessica Sullivan for the use of her lab space, Lorienne Jenstad for training on implementation of the inversion technique, and Xuyang Zhang for statistical assistance. Portions of this article were presented at the American Auditory Society meeting, Scottsdale, Arizona, March 2012 and at the International Hearing Aid Research Conference, Lake Tahoe, California, August 2012.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article. This work was partially supported by the National Institutes of Health (NIDCD 5R01DC012769 and P30DC004661).