Interference suppression techniques

Abstract

System ( 10 ) is disclosed including an acoustic sensor array ( 20 ) coupled to processor ( 42 ). System ( 10 ) processes inputs from array ( 20 ) to extract a desired acoustic signal through the suppression of interfering signals. The extraction/suppression is performed by modifying the array ( 20 ) inputs in the frequency domain with weights selected to minimize variance of the resulting output signal while maintaining unity gain of signals received in the direction of the desired acoustic signal. System ( 10 ) may be utilized in hearing aids, voice input devices, surveillance devices, and other applications.

1 . A method, comprising: 
 detecting acoustic excitation with a number of acoustic sensors, the acoustic sensors providing a corresponding number of sensor signals;    establishing a number of frequency domain components for each of the sensor signals; and    determining an output signal representative of the acoustic excitation from a designated direction, said determining including weighting the components for each of the sensor signals to reduce variance of the output signal and provide a predefined gain of the acoustic excitation from the designated direction.    
   
   
       2 . The method of  claim 1 , wherein said determining includes minimizing the variance of the output signal and the predefined gain is approximately unity.  
   
   
       3 . The method of  claim 1 , further comprising changing the designated direction without moving any of the acoustic sensors and repeating said establishing and said determining after said changing.  
   
   
       4 . The method of  claim 1 , further comprising changing from the designated direction by moving one or more of the acoustic sensors and repeating said establishing and said determining after said changing.  
   
   
       5 . The method of  claim 1 , wherein said components correspond to fourier transforms and said weighting includes calculating a number of weights to minimize the variance of the output signal subject to a constraint that the predefined gain be generally maintained at unity, the weights being determined as a function of a frequency domain correlation matrix and a vector corresponding to the designated direction.  
   
   
       6 . The method of  claim 5 , further comprising recalculating the weights from time to time and repeating said establishing and said determining on an established basis.  
   
   
       7 . The method of  claim 1 , further comprising calculating said weights subject to a constraint of an insubstantial level of gain difference between the acoustic sensors.  
   
   
       8 . The method of  claim 1 , further comprising adjusting a correlation factor to control beamwidth as a function of frequency.  
   
   
       9 . The method of  claim 1 , further comprising calculating a number of correlation matrices and adaptively changing correlation length for one or more of the correlation matrices relative to at least one other of the correlation matrices.  
   
   
       10 . The method of  claim 1 , further comprising tracking location of at least one acoustic signal source as a function of a phase difference between the acoustic sensors.  
   
   
       11 . The method of any of claims  1 - 10 , further comprising providing a hearing aid with the acoustic sensors and a processor operable to perform said establishing and said determining.  
   
   
       12 . The method of any of claims  1 - 10 , wherein a voice input device includes the acoustic sensors and a processor operable to perform said establishing and said determining.  
   
   
       13 . A method, comprising: 
 operating a hearing aid including a number of acoustic sensors in the presence of multiple acoustic sources, the acoustic sensors providing a corresponding number of sensor signals;    monitoring a selected one of the acoustic sources;    determining a set of frequency components for each of the sensor signals; and    generating an output signal representative of the selected one of the acoustic sources, the output signal being a weighted combination of the set of frequency components for each of the sensor signals calculated to minimize variance of the output signal.    
   
   
       14 . The method of  claim 13 , further comprising processing the output signal to provide at least one acoustic output to a user of the hearing aid.  
   
   
       15 . A method, comprising: 
 operating a voice input device including a number of acoustic sensors, the acoustic sensors providing a corresponding number of sensor signals;    determining a set of frequency components for each of the sensor signals; and    generating an output signal representative of acoustic excitation from a designated direction, the output signal being a weighted combination of the set of frequency components for each of the sensor signals calculated to minimize variance of the output signal.    
   
   
       16 . The method of  claim 15 , wherein the voice input device is included in a voice recognition system for a computer.  
   
   
       17 . The method of any of claims  13 - 16 , wherein said generating includes calculating a number of weights as a function of a frequency domain correlation matrix and a vector corresponding to the designated direction.  
   
   
       18 . The method of  claim 17 , further comprising recalculating the weights from time to time.  
   
   
       19 . The method of  claim 17 , further comprising determining the weighted combination of the sensor signals as a function of a gain constraint associated with the designated direction.  
   
   
       20 . The method of  claim 17 , further comprising adjusting a correlation factor to control beamwidth as a function of frequency.  
   
   
       21 . The method of  claim 17 , further comprising adaptively changing correlation length.  
   
   
       22 . A method, comprising: 
 operating a hearing aid including a number of acoustic sensors, the acoustic sensors providing a corresponding number of sensor signals;    selecting a direction to monitor for acoustic excitation with the hearing aid;    determining a set of signal transform components for each of the sensor signals;    calculating a number of weight values as a function of a correlation of the signal transform components, an adjustment factor, and the direction; and    weighting the signal transform components with the weight values to provide an output signal representative of the acoustic excitation emanating from the direction.    
   
   
       23 . The method of  claim 22 , wherein the transform components correspond to different frequencies and the adjustment factor has a first value for a first one of the frequencies and second value different than the first value for a second one of the frequencies to control beamwidth.  
   
   
       24 . The method of  claim 22 , wherein the adjustment factor corresponds to correlation length and further comprising determining a number of different correlations with correlation length adaptively changed in accordance with different values for the adjustment factor.  
   
   
       25 . The method of  claim 22 , further comprising: 
 determining a level of interference; and    adjusting the beamwidth of the hearing aid in response to the level of interference with the adjustment factor.    
   
   
       26 . The method of  claim 22 , further comprising: 
 determining a rate of change of at least one frequency of at least one of the sensor signals with respect to time; and    adjusting the correlation length in response to the rate of change with the adjustment factor.    
   
   
       27 . A method, comprising: 
 operating a hearing aid including a number of acoustic sensors, the acoustic sensors providing a corresponding number of sensor signals;    providing a set of signal transform components for each of the sensor signals;    calculating a number of weight values as a function of a correlation of the transform components for each of a number different frequencies, said calculating including applying a first beamwidth control value for a first one of the frequencies and a second beamwidth control value for a second one of the frequencies different than the first beamwidth control value; and    weighting the signal transform components with the weight values to provide an output signal.    
   
   
       28 . The method of  claim 27 , further comprising selecting the first beamwidth value and the second beamwidth value to provide a generally constant beamwidth of the hearing aid over a predefined frequency range.  
   
   
       29 . The method of  claim 27 , wherein the first beamwidth value and the second beamwidth value differ in accordance with a difference in an amount of interference at the first one of the frequencies relative to the second one of the frequencies.  
   
   
       30 . A method, comprising: 
 operating a hearing aid including a number of acoustic sensors, the acoustic sensors providing a corresponding number of sensor signals;    providing a first plurality of signal transform components for the sensor signals;    calculating a first set of weight values as a function of a first correlation of the first signal transform components corresponding to a first correlation length;    providing a second plurality of signal transform components for the sensor signals;    calculating a second set of weight values as a function of a second correlation of the second signal transform components corresponding to a second correlation length different that the first correlation length; and    generating an output signal as a function of the first weight values and the second weight values.    
   
   
       31 . The method of  claim 30 , wherein the first correlation length and the second correlation length differ in accordance with a difference in rate of change of at least one frequency of at least one of the sensor signals with respect to time.  
   
   
       32 . The method of any of claims  22 - 31 , wherein the number of sensors is two and the hearing aid has a single, monaural output.  
   
   
       33 . The method of any of claims  22 - 31 , wherein said calculating is performed to minimize output variance.  
   
   
       34 . The method of any of claims  22 - 31 , further comprising localizing a selected acoustic source relative to a reference as a function of the transform components.  
   
   
       35 . The method of any of claims  22 - 31 , wherein the transform components are of a fourier type.  
   
   
       36 . A hearing aid system operable to perform the method of any of claims  22 - 31 .  
   
   
       37 . A method comprising: 
 detecting acoustic excitation with a number of acoustic sensors, the acoustic sensors providing a corresponding number of sensor signals;    establishing a set of signal transform components for each of the sensor signals;    tracking location of a source of the acoustic excitation relative to a reference as a function of the transform components; and    providing an output signal as a function of the location and a correlation of the transform components.    
   
   
       38 . The method of  claim 37 , wherein the number of sensors is two and said tracking includes determining a phase difference between the sensor signals.  
   
   
       39 . The method of  claim 37 , wherein the reference is a designated axis and the location is provided in the form of an azimuthal direction.  
   
   
       40 . The method of  claim 37 , wherein said tracking includes generating an array with a number of elements each corresponding to a different azimuth and detecting one or more peak values among the elements of the array.  
   
   
       41 . The method of  claim 37 , further comprising adjusting a beamwidth factor relative to frequency.  
   
   
       42 . The method of  claim 37 , further comprising calculating a number of different correlation matrices and adaptively changing correlation length of one or more of the matrices relative to at least one other of the matrices.  
   
   
       43 . The method of  claim 37 , further comprising steering a direction-indicating vector corresponding to the location.  
   
   
       44 . The method of  claim 37 , wherein said providing include generating the output signal by weighting the transform components to reduce variance of the output signal and provide a predefined gain.  
   
   
       45 . A device operable to perform the method of any of claims  37 - 44 .  
   
   
       46 . A hearing aid system operable to perform the method of any of claims  37 - 44 .  
   
   
       47 . An apparatus, comprising: 
 an acoustic sensor array operable to detect acoustic excitation, said acoustic sensor array including two or more acoustic sensors each operable to provide a respective one of a number of sensor signals; and    a processor operable to determine a set of frequency components for each of said sensor signals and generate an output signal representative of the acoustic excitation from a designated direction, said output signal being calculated from a weighted combination of said set of frequency components for each of said sensor signals to reduce variance of said output signal subject to a gain constraint for the acoustic excitation from said designated direction.    
   
   
       48 . The apparatus of  claim 47 , wherein said processor is operable to calculate said weighted combination to generally minimize said variance of said output signal and generally maintain said gain at unity.  
   
   
       49 . The apparatus of  claim 47 , wherein said processor is operable to determine a number of signal weights as a function of a frequency domain correlation matrix and a vector corresponding to said designated direction.  
   
   
       50 . An apparatus, comprising: 
 a first acoustic sensor operable to provide a first sensor signal;    a second acoustic sensor operable to provide a second sensor signal;    a processor operable to generate an output signal representative of acoustic excitation detected with said first acoustic sensor and said second acoustic sensor from a designated direction, said processor including: 
 means for transforming said first sensor signal to a first number of frequency domain transform components and said second sensor signal to a second number of frequency domain transform components,  
 means for weighting said first transform components to provide a corresponding number of first weighted components and said second transform components to provide a corresponding number of second weighted components as a function of variance of said output signal and a gain constraint for the acoustic excitation from said designated direction,  
 means for combining each of said first weighted components with a corresponding one of said second weighted components to provide a frequency domain form of said output signal; and  
 means for providing a time domain form of said output signal from said frequency domain form.  
   
   
   
       51 . The apparatus of any of claims  47 - 50 , wherein said processor includes means for steering said designated direction.  
   
   
       52 . The apparatus of any of claims  47 - 50 , further comprising at least one acoustic output device responsive to said output signal.  
   
   
       53 . The apparatus of any of claims  47 - 50 , wherein the apparatus is arranged as a hearing aid.  
   
   
       54 . The apparatus of any of claims  47 - 50 , wherein the apparatus is arranged as a voice input device.  
   
   
       55 . The apparatus of any of claims  47 - 50 , wherein said processor is operable to localize an acoustic excitation source relative to a reference.  
   
   
       56 . The apparatus of any of claims  47 - 50 , wherein said processor is operable to track location of an acoustic excitation source relative to an azimuthal plane.  
   
   
       57 . The apparatus of any of claims  47 - 50 , wherein said processor is operable to adjust a beamwidth control parameter with frequency.  
   
   
       58 . The apparatus of any of claims  47 - 50 , wherein said processor is operable to calculate a number of different correlation matrices and adaptively adjust correlation length of one or more of the matrices relative to at least one other of the matrices.