Binary Estimator Selection Methods for Hearing Aids With a Remote Microphone

Using a high signal-to-noise ratio remote microphone (RM) with hearing aids (HAs) is advantageous for HA users. However, the benefit depends significantly on the properties of the wireless channel. While existing literature often assumes an error-free and instantaneous wireless transmission channel, in reality, wireless transmission of audio typically undergoes latency, which introduces a time difference of arrival (TDOA) between the local HA microphone signals and the wirelessly transmitted RM signal received at the HA. We first observe that, as the distance between the HAs and the RM increases, the TDOAs decrease, making the signals received from a distant RM more beneficial than those from a nearby RM. Next, we propose two methods to combine a RM signal with the HA, under realistic TDOAs. Acting in either the complex spectral domain or the magnitude spectral domain, the methods make a binary selection in each time-frequency component between minimum mean-square-error estimates determined from the HA microphone signals and RM signal, respectively. We evaluate the performance of the resulting estimate in terms of their signal quality and speech intelligibility using objective and subjective tests. We show that the proposed methods outperform their baselines that use only HA signals, for TDOAs in the range of 30-60 ms.