  This work presents a method for designing the weighting parameter required by
Wiener-based binaural noise reduction methods. This parameter establishes the
desired tradeoff between noise reduction and binaural cue preservation in
hearing aid applications. The proposed strategy was specially derived for the
preservation of 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 to signal to noise ratio (SNR) variations. A theoretical framework, based on
the mathematical definition of the homogeneity degree, is presented and applied
to a generic augmented Wiener-based cost function. The theoretical insights
obtained are supported bycomputational simulations and psychoacoustic
experiments using the multichannel Wiener filter with interaural transfer
function preservation technique (MWF-ITF), as a case study. Statistical
analysis indicates that the proposed dynamic structure for the weighting
parameter and the design method of its fixed part provide significant
robustness against changes in the original binaural cues of both speech and
residual noise, at the cost of a small decrease in the noise reduction
performance, as compared to the use of a purely fixed weighting parameter.
