Showing papers on "Microphone array published in 1977"
TL;DR: In this article, the first and second speech signals are aligned in phase by electronic delay adjustment using a pair of microphones or using vertical arrays of microphones, and phase alignment by feedback servo control of a rotatable microphone array.
Abstract: A circuit for reducing reverberative interference utilizes a pair of spatially separated microphones to obtain speech signals from a common sound source. Each speech signal is transformed into an envelope representative signal having rapid increases responsive to direct path and echo energy bursts from the sound source and exponential decaying portions between energy bursts. A first pulse corresponding to a sound source direct path energy burst is generated responsive to the first speech signal exceeding its envelope representative signal, and further first pulses corresponding to echo bursts are inhibited for a predetermined time. A second pulse corresponding to said sound source direct path energy burst is generated responsive to the second speech signal exceeding its envelope representative signal, and further second pulses corresponding to echo bursts are inhibited for a predetermined time. The first and second speech signals are aligned in phase responsive to the time difference between said first and second pulses. Three embodiments are disclosed: phase alignment by electronic delay adjustment using a pair of microphones or using vertical arrays of microphones, and phase alignment by feedback servo control of a rotatable microphone array.
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