Abstract
Modern binaural hearing aids utilize multimicrophone speech enhancement algorithms to enhance signals in terms of signal-to-noise ratio, but they may distort the interaural cues that allow the user to localize sources, in particular, suppressed interfering sources or background noise. In this paper, we present a novel algorithm that enhances the target signal while aiming to maintain the correct spatial rendering of both the target signal as well as the background noise. We use a bimodal approach, where a signal-to-noise ratio (SNR) estimator controls a binary decision mask, switching between the output signals of a binaural minimum variance distortionless response (MVDR) beamformer and scaled reference microphone signals. We show that the proposed selective binaural beamformer (SBB) can enhance the target signal while maintaining the overall spatial rendering of the acoustic scene.
Highlights
Situations where we are exposed to a number of sound sources reaching our ears simultaneously are part of our everyday life
4 Evaluation Using the binaural database presented in [32], we simulate noisy and reverberant microphone signals by convolving clean speech samples from the Oldenburger Satztest (OLSA) database [33,34,35], with room impulse responses measured on an artificial head and by adding noise recorded by the same setup in the same room
4.1.1 Influence of misestimating the steering vector Since the selective binaural beamformer (SBB) requires an estimate of the direction of arrival (DOA) of the target source for both the underlying minimum variance distortionless response (MVDR) beamformer and to estimate the signal-to-noise ratio (SNR), we evaluate the influence of misestimating the steering vector dT on the intelligibility weighted SNR (iSNR)
Summary
Situations where we are exposed to a number of sound sources reaching our ears simultaneously are part of our everyday life. Miniaturization has allowed modern hearing aids to utilize multiple microphones in compact devices, allowing the use of multimicrophone signal enhancement algorithms [9,10,11,12] Methods such as fixed and adaptive beamforming and multichannel Wiener filtering are generally capable of better noise suppression and lower speech distortion than single-channel methods [9, 11]. We suggest a bimodal processing paradigm: (a) where the target is dominant, use signal enhancement that preserves the interaural cues of the target; (b) where the background noise is dominant, pass the acoustic signal to the output unmodified save by attenuation We realize this bimodal processing by using a binary decision mask in the spectro-temporal plane, i.e., within each frequency band and time frame, the signals presented to the ears are either the enhanced (binaural) target signal or the attenuated background noise (taken from two reference microphones, located near the respective ear). When subjects compared the spatial rendering of the overall acoustic scene, we find that, in situations where the beamformer target is off the center direction, our proposed algorithm preserves the spatial image better than the algorithms to which it was compared
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