In this paper, we propose a new microphone array signal processing technique, which increases the number of\nmicrophones virtually by generating extra signal channels from real microphone signals. Microphone array signal\nprocessing methods such as speech enhancement are effective for improving the quality of various speech\napplications such as speech recognition and voice communication systems. However, the performance of speech\nenhancement and other signal processing methods depends on the number of microphones. Thus, special\nequipment such as a multichannel A/D converter or a microphone array is needed to achieve high processing\nperformance. Therefore, our aim was to establish a technique for improving the performance of array signal processing\nwith a small number of microphones and, in particular, to increase the number of channels virtually by synthesizing\nvirtual microphone signals, or extra signal channels, from two channels of microphone signals. Each virtual microphone\nsignal is generated by interpolating a short-time Fourier transform (STFT) representation of the microphone signals.\nThe phase and amplitude of the signal are interpolated individually. The phase is linearly interpolated on the basis of a\nsound propagation model, and the amplitude is nonlinearly interpolated on the basis of �² divergence. We also\nperformed speech enhancement experiments using a maximum signal-to-noise ratio (SNR) beamformer equipped\nwith virtual microphones and evaluated the improvement in performance upon introducing virtual microphones.
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