Robust parameter strategy for Wiener-based binaural noise reduction methods in hearing aids

Abstract

This work presents a method for designing the weighting parameter required for Wiener-based binaural noise reduction methods. This parameter establishes the desired trade-off between noise reduction and binaural cue preservation in hearing aids. The proposed strategy was specially derived for the preservation of the interaural level difference, interaural time difference and interaural coherence binaural cues. It is defined as a function of the average input noise power at the microphones, providing robustness against the influence of joint changes in noise and speech power (Lombard effect), as well as signal-to-noise ratio variations. A theoretical framework based on the mathematical definition of the degree of homogeneity is presented and applied to a generic augmented Wiener-based cost function. The theoretical insights obtained are supported by computational simulations and psychoacoustic experiments using the multichannel Wiener filter with a noise interaural transfer function preservation technique (MWF-ITFv), as a case study. Statistical analysis indicates that, compared to a purely fixed weighting parameter, the proposed structure for the weighting parameter and the design method of its fixed part provide significant robustness against changes in the noise binaural cues at the cost of a small noise reduction performance decrease and speech binaural cue distortion.