Estimating direction of arrival from plural microphones
First Claim
1. A method for suppressing noise in a communication device having at least first and second microphones and a direction of arrival circuit coupled to the microphones, said method comprising the steps of:
- providing first and second variable gain circuits for the first microphone, the gain of the first and second variable gain circuits being adjustable, each of the first and second variable gain circuits providing an output;
providing third and fourth variable gain circuits for the second microphone, the gain of the third and fourth variable gain circuits being adjustable, each of the third and fourth variable gain circuits providing an output;
adjusting the gain of the first, second, third and fourth variable gain circuits based on data from the direction of arrival circuit, said adjusting step including the steps of;
calibrating the first and third variable gain circuits during the presence of a desired signal;
calibrating the second and fourth variable gain circuits during the presence of an interfering signal; and
combining the outputs from the first, second, third and fourth variable gain circuits.
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Accused Products
Abstract
A noise suppression system includes plural microphones, a fixed beam former, a blocking matrix, plural adaptive filters, and a direction of arrival circuit coupled to the adaptive filters that prevents the filters from adapting in the presence of a signal in the look direction. The direction of arrival circuit causes the filters to adapt more quickly in the absence of a signal in the look direction. A pair of adjustable gain circuits is coupled to each microphone. A first adjustable gain circuit from each pair is calibrated during the presence of a desired signal and a second adjustable gain circuit from each pair is calibrated during the presence of an interfering signal. A fixed null-forming circuit is coupled to a first pair of variable gain circuits and an adaptive null forming circuit is coupled to a second pair of adjustable gain circuits. The ratio of the gains of the null forming circuits is used as a control signal. Successive ratios are averaged with a variable smoothing constant and a control signal is derived from the averaged ratios.
43 Citations
17 Claims
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1. A method for suppressing noise in a communication device having at least first and second microphones and a direction of arrival circuit coupled to the microphones, said method comprising the steps of:
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providing first and second variable gain circuits for the first microphone, the gain of the first and second variable gain circuits being adjustable, each of the first and second variable gain circuits providing an output; providing third and fourth variable gain circuits for the second microphone, the gain of the third and fourth variable gain circuits being adjustable, each of the third and fourth variable gain circuits providing an output; adjusting the gain of the first, second, third and fourth variable gain circuits based on data from the direction of arrival circuit, said adjusting step including the steps of; calibrating the first and third variable gain circuits during the presence of a desired signal; calibrating the second and fourth variable gain circuits during the presence of an interfering signal; and combining the outputs from the first, second, third and fourth variable gain circuits.
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2. A method for suppressing noise in a communication device having plural microphones, said method comprising the steps of:
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providing a first null-forming circuit coupled to the microphones, the first null-forming circuit providing a first null-forming output; averaging the signals from the microphones to produce an average; determining the gain of the first null-forming circuit as the ratio of the first null-forming output to the average; and using data representing the gain of the first null-forming circuit as a control signal in a noise suppression circuit. - View Dependent Claims (3, 4, 5)
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6. A noise suppression system comprising in combination:
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a first microphone; a second microphone; a fixed beam former coupled to the first microphone and to the second microphone; a blocking matrix coupled to the first microphone and to the second microphone; at least one adaptive filter coupled to the blocking matrix; a subtraction circuit coupled to the output of the fixed beam former and to the output of the at least one adaptive filter; a direction of arrival circuit, coupled to said first microphone, to said second microphone, and to said at least one adaptive filter, the direction of arrival circuit preventing the at least one adaptive filter from adapting in the presence of a signal in the look direction of the direction of arrival circuit; a first pair of adjustable gain circuits for the first microphone; and a second pair of adjustable gain circuits for the second microphone. - View Dependent Claims (7, 8, 9, 10, 11, 12)
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13. A noise suppression system comprising in combination:
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a first microphone; a second microphone; a fixed beam former coupled to the first microphone and to the second microphone; a blocking matrix coupled to the first microphone and to the second microphone; at least one adaptive filter coupled to the blocking matrix; a subtraction circuit coupled to the output of the fixed beam former and to the output of the at least one adaptive filter; a direction of arrival circuit, coupled to said first microphone, to said second microphone, and to said at least one adaptive filter, the direction of arrival circuit preventing the at least one adaptive filter from adapting in the presence of a signal in the look direction of the direction of arrival circuit; and a single channel signal processing circuit having an adaptation rate, wherein information from the direction of arrival circuit controls the adaptation rate of the single channel signal processing circuit. - View Dependent Claims (14)
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15. A circuit for identifying the presence of a desired signal, said circuit comprising:
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a first input coupled to a source of desired signal; a second input coupled to a source of interfering signal; a first null former coupled to the first input and to the second input and having a first output; a first averaging circuit coupled to the first input and to the second input and having a second output; a first ratio detector coupled to the first output and to the second output and producing a first ratio signal representing the ratio of the signals on the first output and the second output. - View Dependent Claims (16, 17)
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Specification