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Audio signals from any array of microphones are individually filtered, delayed, and scaled in order to form an acoustic beam that focuses the array on a particular region. Nonlinear robust signal estimation processing is applied to the resulting set of audio signals to generate an output signal for

Audio signals from any array of microphones are individually filtered, delayed, and scaled in order to form an acoustic beam that focuses the array on a particular region. Nonlinear robust signal estimation processing is applied to the resulting set of audio signals to generate an output signal for the array. The nonlinear robust signal estimation processing may involve dropping or otherwise reducing the magnitude of one or more of the highest and lowest data in each set of values from the resulting audio signals and then selecting the median from or generating an average of the remaining values to produce a representative, central value for the output audio signal. The nonlinear robust signal estimation processing effectively discriminates against noise originating at an unknown location outside of the focal region of the acoustic beam.

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What is claimed is: 1. A method for processing audio signals generated by an array of two or more microphones, comprising the steps of: (a) filtering by delaying and scaling the audio signal from at least one microphone to generate a processed audio signal for each microphone; and (b) combining the

What is claimed is: 1. A method for processing audio signals generated by an array of two or more microphones, comprising the steps of: (a) filtering by delaying and scaling the audio signal from at least one microphone to generate a processed audio signal for each microphone; and (b) combining the processed audio signals for the two or more microphones in a nonlinear manner that suppresses effects of high values to form an acoustic beam that focuses the array on one or more desired regions in space by performing nonlinear signal estimation processing on the processed audio signals from the microphones to generate an output signal for the array, wherein: the nonlinear signal estimation processing discriminates against noise originating at an unknown location outside of the one or more desired regions; and the nonlinear signal estimation processing picks a representative, central value from the processed audio signals for the two or more microphones, by altering at least one extreme value from at least one of the processed audio signals for the two or more microphones. 2. The invention of claim 1, wherein step (a) comprises the step of applying a digital filter corresponding to the inverse of each transfer function from a desired focal point to each microphone to compensate for reverberation in a volume containing the array. 3. The invention of claim 1, wherein the output signal is processed in a feedback loop to generate control signals that adjust the nonlinear signal estimation processing of step (b). 4. The invention of claim 3, wherein the control signals adjust weights applied to the processed audio signals during the nonlinear signal estimation processing of step (b). 5. The invention of claim 4, wherein a weight for each processed audio signal is based on a ratio of power in a speech band to power outside the speech band for the processed audio signal. 6. The invention of claim 3, wherein the output signal is processed in another feedback loop to generate other control signals that adjust the filtering of step (a) to attempt to match each of the processed audio signals. 7. The invention of claim 1, wherein the output signal is processed in a feedback loop to generate control signals that adjust the filtering of step (a). 8. The invention of claim 1, wherein the filtering of step (a) is dynamically adjusted to attempt to match each of processed audio signals. 9. The invention of claim 8, wherein the filtering of step (a) is dynamically adjusted to attempt to match each of the processed audio signals in amplitude and phase to each other and to the output signal. 10. The invention of claim 1, wherein the nonlinear signal estimation processing comprises the step of selecting the representative, central value as a median of the processed audio signals. 11. The invention of claim 1, wherein the nonlinear signal estimation processing comprises the steps of: (1) adjusting the magnitude of one or more of at least one of the highest and lowest values of the processed audio signals to generate a set of adjusted audio signals; and (2) selecting the representative, central value as a median or average of the adjusted audio signals. 12. The invention of claim 11, wherein: step (1) comprises the steps of: (i) adjusting the value of the n highest values down to match the (n+1)th highest data value, where n is a non-negative integer; and (ii) adjusting the value of the m lowest values up to match the (m+1)th lowest data value, where m is a non-negative integer; and step (2) comprises the step of selecting the representative, central value as an average of the processed audio signals. 13. The invention of claim 12, wherein the average is a weighted average. 14. The invention of claim 1, wherein the nonlinear signal estimation processing comprises the steps of: (1) dropping one or more of the highest and lowest values of the processed audio signals to generate a set of adjusted audio signals; and (2) selecting the representative, central value as an average of the adjusted audio signals. 15. The invention of claim 14, wherein the average is a weighted average. 16. The invention of claim 1, wherein the nonlinear signal estimation processing treats each set of input values for the processed audio signals independently. 17. The invention of claim 1, wherein the nonlinear signal estimation processing is based on multiple values from each processed audio signal over a period of time. 18. The invention of claim 17, wherein the nonlinear signal estimation processing comprises the step of applying temporal filtering to the input values of each processed audio signal. 19. The invention of claim 18, wherein the nonlinear signal estimation processing further comprises the steps of generating a distance measure between pairs of audio signals and generating the output signal from the one or more audio signals having the smallest distance measures with other audio signals. 20. A machine-readable medium, having encoded thereon program code, wherein, when the program code is executed by a machine, the machine implements a method for processing audio signals generated by an array of two or more microphones, comprising the steps of: (a) filtering by delaying and scaling the audio signal from at least one microphone to generate a processed audio signal for each microphone; and (b) combining the processed audio signals for the two or more microphones in a nonlinear manner that suppresses effects of high values to form an acoustic beam that focuses the array on one or more desired regions in space by performing nonlinear signal estimation processing on the processed audio signals from the microphones to generate an output signal for the array, wherein: the nonlinear signal estimation processing discriminates against noise originating at an unknown location outside of the one or more desired regions; and the nonlinear signal estimation processing picks a representative, central value from the processed audio signals for the two or more microphones, by altering at least one extreme value from at least one of the processed audio signals for the two or more microphones. 21. A method for processing audio signals generated by an array of two or more microphones, comprising the steps of: (a) filtering by delaying and scaling the audio signal from at least one microphone to generate a processed audio signal for each microphone; and (b) combining the processed audio signals for the two or more microphones in a nonlinear manner to form an acoustic beam that focuses the array on one or more desired regions in space by performing nonlinear signal estimation processing on the processed audio signals from the microphones to generate an output signal for the array, wherein the nonlinear signal estimation processing discriminates against noise originating at an unknown location outside of the one or more desired regions, wherein the output signal is processed in a feedback loop to generate control signals that adjust the nonlinear signal estimation processing of step (b). 22. The invention of claim 21, wherein the control signals adjust weights applied to the processed audio signals during the nonlinear signal estimation processing of step (b). 23. The invention of claim 22, wherein a weight for each processed audio signal is based on a ratio of power in a speech band to power outside the speech band for the processed audio signal. 24. The invention of claim 21, wherein the output signal is processed in another feedback loop to generate other control signals that adjust the filtering of step (a) to attempt to match each of the processed audio signals. 25. A method for processing audio signals generated by an array of two or more microphones, comprising the steps of: (a) filtering by delaying and scaling the audio signal from at least one microphone to generate a processed audio signal for each microphone; and (b) combining the processed audio signals for the two or more microphones in a nonlinear manner to form an acoustic beam that focuses the array on one or more desired regions in space by performing nonlinear signal estimation processing on the processed audio signals from the microphones to generate an output signal for the array, wherein the nonlinear signal estimation processing discriminates against noise originating at an unknown location outside of the one or more desired regions, wherein the output signal is processed in a feedback loop to generate control signals that adjust the filtering of step (a). 26. The invention of claim 25, wherein the fitering of step (a) is dynamically adjusted to attempt to match each of the processed audio signals. 27. The invention of claim 26, wherein the filtering of step (a) is dynamically adjusted to attempt to match each of the processed audio signals in amplitude and phase to each other and to the output signal. 28. A method for processing audio signals generated by an array of two or more microphones, comprising the steps of: (a) filtering by delaying and scaling the audio signal from at least one microphone to generate a processed audio signal for each microphone; and (b) combining the processed audio signals for the two or more microphones in a nonlinear manner to form an acoustic beam that focuses the array on one or more desired regions in space by performing nonlinear signal estimation processing on the processed audio signals from the microphones to generate an output signal for the array, wherein the nonlinear signal estimation processing discriminates against noise originating at an unknown location outside of the one or more desired regions, wherein the nonlinear signal estimation processing picks a representative, central value from the processed audio signals for the two or more microphones, by altering at least one extreme value from at least one of the processed audio signals for the two or more microphones, wherein the nonlinear signal estimation processing comprises the steps of: (1) adjusting the magnitude of one or more of at least one of the highest and lowest values of the processed audio signals for the two or more microphones to generate a set of adjusted audio signals; and (2) selecting the representative, central value as a median or average of the adjusted audio signals. 29. The invention of claim 28, wherein the nonlinear signal estimation processing comprises the step of selecting the representative, central value as a median of the processed audio signals. 30. The invention of claim 28, wherein: step (1) comprises the steps of: (i) adjusting the value of the n highest values down to match the (n+1)th highest data value, where n is a non-negative integer; and (ii) adjusting the value of the m lowest values up to match the (m+1)th lowest data value, where m is a non-negative integer; and step (2) comprises the step of selecting the representative, central value as an average of the processed audio signals. 31. The invention of claim 30, wherein the average is a weighted average. 32. A method for processing audio signals generated by an array of two or more microphones, comprising the steps of: (a) filtering the audio signal from each microphone to generate a processed audio signal for each microphone; and (b) combining the processed audio signals in a nonlinear manner to form an acoustic beam that focuses the array on one or more desired regions in space by performing nonlinear signal estimation processing on the processed audio signals from the microphones to generate an output signal for the array, wherein the nonlinear signal estimation processing discriminates against noise originating at an unknown location outside of the one or more desired regions, wherein: the nonlinear signal estimation processing is based on multiple values from each processed audio signal over a period of time; and the nonlinear signal estimation processing comprises the steps of: applying temporal filtering to the input values of each processed audio signal; generating a distance measure between pairs of audio signals; and generating the output signal from the one or more audio signals having the smallest distance measures to attempt to match each of the processed audio signals. 33. A method for processing audio signals generated by an array of two or more microphones, comprising the steps of: (a) filtering the audio signal from each microphone to generate a processed audio signal for each microphone; and (b) combining the processed audio signals in a nonlinear manner to form an acoustic beam that focuses the array on one or more desired regions in space by performing nonlinear signal estimation processing on the processed audio signals from the microphones to generate an output signal for the array, wherein the nonlinear signal estimation processing discriminates against noise originating at an unknown location outside of the one or more desired regions, wherein the nonlinear signal estimation processing picks a representative, central value from the processed audio signals, by altering at least one extreme value from at least one of the processed audio signals, wherein the nonlinear signal estimation processing comprises the steps of: (1) dropping one or more of the highest and lowest values of the processed audio signals to generate a set of adjusted audio signals; and (2) selecting the representative, central value as an average of the adjusted audio signals. 34. The invention of claim 33, wherein the average is a weighted average. 35. A method for processing audio signals generated by an array of two or more microphones, comprising the steps of: (a) filtering by delaying and scaling the audio signal from at least one microphone to generate a processed audio signal for each microphone; and (b) combining the processed audio signals for the two or more microphones in a nonlinear manner that suppresses effects of high values to form an acoustic beam that focuses the array on one or more desired regions in space by performing nonlinear signal estimation processing on the processed audio signals from the microphones to generate an output signal for the array, wherein: the nonlinear signal estimation processing discriminates against noise originating at an unknown location outside of the one or more desired regions; and the filtering of step (a) is dynamically adjusted to attempt to match each of the processed audio signals in amplitude and phase to each other and to the output signal. 36. A method for processing audio signals generated by an array of two or more microphones, comprising the steps of: (a) filtering the audio signal from each microphone to generate a processed audio signal for each microphone; and (b) combining the processed audio signals in a nonlinear manner that suppresses effects of high values to form an acoustic beam that focuses the array on one or more desired regions in space by performing nonlinear signal estimation processing on the processed audio signals from the microphones to generate an output signal for the array, wherein: the nonlinear signal estimation processing discriminates against noise originating at an unknown location outside of the one or more desired regions; the nonlinear signal estimation processing picks a representative, central value from the processed audio signals, by altering at least one extreme value from at least one of the processed audio signals; and step (a) comprises the step of applying a digital filter corresponding to the inverse of each transfer function from a desired focal point to each microphone to compensate for reverberation in a volume containing the array.