Acoustic and perceptual effects of magnifying interaural difference cues in a simulated “binaural” hearing aid

Abstract

Objective: To investigate the influence of an algorithm designed to enhance or magnify interaural difference cues on speech signals in noisy, spatially complex conditions using both technical and perceptual measurements. To also investigate the combination of interaural magnification (IM), monaural microphone directionality (DIR), and binaural coherence-based noise reduction (BC). Design: Speech-in-noise stimuli were generated using virtual acoustics. A computational model of binaural hearing was used to analyse the spatial effects of IM. Predicted speech quality changes and signal-to-noise-ratio (SNR) improvements were also considered. Additionally, a listening test was carried out to assess speech intelligibility and quality. Study sample: Listeners aged 65–79 years with and without sensorineural hearing loss (N = 10 each). Results: IM increased the horizontal separation of concurrent directional sound sources without introducing any major artefacts. In situations with diffuse noise, however, the interaural difference cues were distorted. Preprocessing the binaural input signals with DIR reduced distortion. IM influenced neither speech intelligibility nor speech quality. Conclusions: The IM algorithm tested here failed to improve speech perception in noise, probably because of the dispersion and inconsistent magnification of interaural difference cues in complex environments.

Key Words:

• Hearing aids
• speech perception
• psychoacoustics/hearing science
• noise
• binaural hearing
• binaural enhancement
• noise reduction

Acknowledgements

This work was supported by the German Research Foundation (DFG) grant “Individualised Hearing Acoustics” [grant number 1732] and by the DFG Cluster of Excellence “Hearing4all” [grant number 1077/1]. Parts of it were presented at the 2014 Annual Meeting of the German Audiological Society, Oldenburg, Germany, March 2014.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

Notes

Notes

1. Anechoic HRIRs were used for the two speakers because reverberant HRIRs were unavailable for the positions of interest.

2. As discussed in “Binaural hearing model” Section, the auditory perception of the noise source was that of a completely lateralised source, so the binaural model does not take this effect into account. To avoid the uncertainty associated with large azimuth angles, all measurements were conducted in such a way that the source signals were not magnified to >90° azimuth.