Reduced-bandwidth Multi-channel Wiener Filter based binaural noise reduction and localization cue preservation in binaural hearing aids

• Two novel reduced-bandwidth noise reduction procedures for binaural hearing aids (wirelessly connected hearing aids) are proposed.
• The procedures are based on the Speech Distortion Weighted Multi-channel Wiener Filter (SDW-MWF) noise reduction technique.
• The procedures preserve the binaural localization cues, which are important for human sound localization and speech intelligibility.
• The procedures take into account the bandwidth constraints of the wireless link.
• Experiments in a reverberant room demonstrate that the procedures can preserve the localization cues without severely degrading the noise reduction performance.

Binaural hearing aids allow for a wireless exchange of microphone signals between a left and a right device. A significant noise reduction performance improvement can be achieved compared to a monaural configuration (a single device) or a bilateral configuration (in which the devices work independently). In addition, the binaural localization cues, i.e. the Interaural Time Differences and Interaural Level Differences, can also be better preserved in a binaural procedure. It was previously proven that a binaural noise reduction procedure based on the Speech Distortion Weighted Multi-channel Wiener Filter (SDW-MWF) indeed preserves the speech localization cues, if all microphone signals can be exchanged. However, in practice, it may not be feasible to exchange all microphone signals between the devices, so that reduced-bandwidth SDW-MWF schemes (where only filtered combinations of microphone signals are exchanged) have to be utilized. This paper demonstrates that a straightforward reduced-bandwidth SDW-MWF scheme still preserves the speech ITD cues, but distorts the speech ILD cues, in a single speech source scenario. Novel reduced-bandwidth SDW-MWF schemes, which make use of a common spectral postfilter, are therefore introduced. Experiments in a reverberant environment demonstrate that the novel schemes reduce the ILD distortion, without severely degrading the noise reduction performance.