Multi-Channel Noise Reduction in Hearing Aids with Wireless Access to an External Reference Signal

Abstract:
The standard scenario for multi-channel noise reduction in a hearing aid (HA) is a scenario with one desired speech signal in background noise. In this case, the on/off phases of the desired speech signal are detected and exploited to estimate the covariance matrices required in the noise reduction algorithms, namely the covariance matrix of the background noise and the covariance matrix of the desired speech signal. These matrices can then be used to construct a so-called Speech Distortion Weighted Multi-channel Wiener Filter (SDW-MWF). In this paper, we consider a more general scenario, where next to the desired speech signal there is also a second desired signal played by an audio device, such as, e.g., a TV set. We assume that this second source signal is transmitted to the HA over a wireless link. While the desired speech signal is an on/off signal, the second desired signal may be continuously active. This in particular disallows adopting the usual covariance matrix estimation procedures. It will be demonstrated how the external reference signal, together with the on/off phases of the desired speech signal, can be exploited to estimate the required covariance matrices to compute the SDWMWF. This is done by decomposing the general SDW-MWF into two subproblems; a single-channel least squares (LS) filtering and a rank-1 SDW-MWF (R1-MWF). We will provide simulations that compare two different implementations of this decomposition. Index Terms — multi-channel noise reduction, speech enhancement, wireless hearing aids