Microphone array processing system for noisy multipath environments
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Abstract
Apparatus and a corresponding method for processing speech signals in a noisy reverberant environment, such as an automobile. An array of microphones (10) receives speech signals from a relatively fixed source (12) and noise signals from multiple sources (32) reverberated over multiple paths. One of the microphones is designated a reference microphone and the processing system includes adaptive frequency impulse response (FIR) filters (24) enabled by speech detection circuitry (21) and coupled to the other microphones to align their output signals with the reference microphone output signal. The filtered signals are then combined in a summation circuit (18). Signal components derived from the speech signal combine coherently in the summation circuit, while noise signal components combine incoherently, resulting in composite output signal with an improved signal-to-noise ratio. The composite output signal is further processed in a speech conditioning circuit (20) to reduce the effects of reverberation.
22 Citations
31 Claims
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1-10. -10. (canceled)
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11. A microphone array processing system for performance enhancement in noisy environments, the system comprising:
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a plurality of N microphones positioned to detect speech from a speech source and noise from at least one noise source and to generate corresponding microphone output signals, where N is a positive integer denoting a number of the plurality of microphones, one of the N microphones being designated a reference microphone and the other N−
1 microphones being designated data microphones, the reference microphone and the data microphones receive acoustic signals both from the speech source and from the at least one noise source;
a plurality of adaptive filters, one for each of the data microphones, for aligning each data microphone output signal relative to the reference microphone output signal; and
a signal summation circuit that sums the adaptively filtered microphone output signals with the reference microphone output signal such that signal components resulting from the speech source combine coherently to provide a speech signal having a power gain of approximately N2 and such that the signal components resulting from noise combine incoherently to provide a noise signal having power gain of approximately N to produce a corresponding increased signal-to-noise ratio. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A system for improving detection of speech signals, the system comprising:
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a plurality of bandpass filters that remove a known spectral band containing noise from a plurality of microphone output signals to provide corresponding bandpass filtered output signals, the plurality of microphone output signals corresponding to acoustic signals both from a speech source and from at least one noise source, one of the plurality of microphone output signals designated a reference microphone signal and the other microphone output signals being data microphone signals;
a plurality of adaptive filters, one for each of the data microphone output signals, that adaptively filter respective bandpass filtered output signals for each of the data microphone output signals and provide adaptively filtered output signals that are aligned relative to the reference microphone signal; and
a signal summation circuit that sums the adaptively filtered output signals such that speech signal contributions from the data microphones are added coherently to provide a speech output signal having an amplitude gain that approximates a number of the signals being summed by the signal summation circuit and such that signal components resulting from noise combine incoherently to provide a noise signal having an amplitude gain of approximately a square root of the number of the signals being summed by the signal summation circuit to produce a corresponding increased signal-to-noise ratio. - View Dependent Claims (24, 25, 26, 27, 28, 29)
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30. A method for improving detection of speech signals, the method comprising:
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receiving a plurality of microphone output signals from a plurality of microphones positioned to detect speech from a single speech source and noise from at least one noise source, one of the microphone output signals being designated a reference microphone output signal and the others being designated data microphone output signals, wherein plurality of microphone output signals correspond to acoustic signals both from the speech source and from the at least one noise source;
filtering the microphone output signals in a plurality of bandpass filters to eliminate from the microphone output signals a known spectral band containing noise;
adaptively filtering the microphone output signals to align each of the data microphone output signals with the reference microphone output signal; and
combining the adaptively filtered microphone output signals by adding the signal contributions from the speech source coherently to provide a speech amplitude gain that is proportional to a number of signals being added together and by adding the signal components resulting from noise incoherently to provide a noise amplitude gain that is proportional to the square root of the number of signals being added together, whereby a corresponding increased signal-to-noise ratio is produced. - View Dependent Claims (31)
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Specification