The present invention relates to adaptive beamforming in audio systems. More specifically, aspects of the invention relate to a method for adaptively estimating a target sound signal by establishing a simulation model simulating an audio environment comprising: a plurality of spatially separated mic
The present invention relates to adaptive beamforming in audio systems. More specifically, aspects of the invention relate to a method for adaptively estimating a target sound signal by establishing a simulation model simulating an audio environment comprising: a plurality of spatially separated microphones, a target sound source, and a number of audio noise sources.
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1. A method for adaptively estimating a target sound signal, the method comprising: establishing a simulation model simulating an audio environmentcomprising: a plurality of spatially separated microphones,a target sound source, anda number of audio noise sources;setting an initial value for each of
1. A method for adaptively estimating a target sound signal, the method comprising: establishing a simulation model simulating an audio environmentcomprising: a plurality of spatially separated microphones,a target sound source, anda number of audio noise sources;setting an initial value for each of one or more variables, each variable parameterising a comparison of audio signals received at a respective first one of the plurality of microphones with audio signals received at a respective second one of the plurality of microphones;in dependence on dynamic changes in the comparison of audio signals received by the plurality of microphones, iteratively updating the value of said one or more variables;using the updated value of said one or more variables to determine a respective adaptive beamforming weight for each of the plurality of microphones; andsumming the audio signals received by each of the plurality of microphones according to their respective beamformer weights to produce an estimate of the target sound signal. 2. An adaptive beamforming system for estimating a target sound signal in an audio environment comprising a target sound source and a number of audio noise sources, the system comprising: a plurality of spatially separated microphones;a beamformer unit to which signals received by the plurality of microphones are input, and which is configured to estimate the target sound signal by summing the signals from the plurality of microphones according to beamformer weights; andan optimization unit to which the output of the beamformer unit is input, and which is configured to output a control signal to the beamformer unit which adaptively adjusts the beamformer weights;wherein the optimization unit is configured to: set an initial value for each of one or more variables, each variable parameterising a comparison of audio signals received at a respective first one of the plurality of microphones with audio signals received at a respective second one of the plurality of microphones;in dependence on dynamic changes in the comparison of audio signals received by the plurality of microphones, iteratively updating the value of said one or more variables; anduse the updated value of said one or more variables to construct the control signal. 3. A system as claimed in claim 2, further comprising a single channel post-filter configured to produce an estimate of the target sound source power from the beamformer unit output. 4. A system as claimed in claim 2, wherein one of the one or more variables parameterises the difference in the amplitude of the target sound signal received by each of the plurality of microphones compared to one of the plurality of microphones designated as a reference microphone. 5. A system as claimed in claim 2, wherein the initial value of at least one of said one or more variables is set according to a far-field approximation. 6. A system as claimed in claim 4, wherein the variable parameterising the difference in the amplitude of the target sound signal received by each of the plurality of microphones compared to one of the plurality of microphones designated as a reference microphone is limited to plus or minus less than a tenth of its initial value. 7. A system as claimed in claim 2, wherein for one or more of the one or more variables the comparison is with respect to the quality of the audio signals received at the respective first and second ones of the plurality of microphones. 8. A system as claimed in claim 7, wherein for one or more of the one or more variables the comparison is with respect to an estimation of the net signal received at each of the respective first and second ones of the plurality of microphones from the number of audio noise sources. 9. A system as claimed in claim 8, wherein for one or more of the one or more variables the first one of the plurality of microphones is the same as the second one of the plurality of microphones. 10. A system as claimed in claim 9, wherein one or more of the one or more variables parameterises an average degree of self-correlation of: the net signal received by one of the plurality of microphones from the number of audio noise sources; oran average of the net signals received by the plurality of microphones from the number of audio noise sources. 11. A system as claimed in claim 8, wherein for one or more of the one or more variables the first one of the plurality of microphones is different to the second one of the plurality of microphones. 12. A system as claimed claim 11, wherein one or more of the one or more variables parameterises a degree of cross correlation of the net signal received by each respective first one of the plurality of microphones from the number of audio noise sources with the net signal received by each respective second one of the plurality of microphones from the number of audio noise sources. 13. A system as claimed in claim 7, wherein the initial value of each of the said one or more variables is set such that an initial estimation of the correlation matrix formed by cross correlating the estimated net signals received by each of the plurality of microphones from the number of audio noise sources with each other is equal to the diffuse noise correlation matrix for said plurality of spatially separated microphones. 14. A system as claimed in claim 10, wherein the variable parameterising the average degree of self-correlation of the net signal received by one of the plurality of microphones from the number of audio noise sources is limited to be greater than or equal to unity and less than or equal to approximately 100. 15. A system as claimed in claim 12, wherein the one or more variables parameterising the degree of cross correlation of the net signal received by each respective first one of the plurality of microphones from the number of audio noise sources with the net signal received by each respective second one of the plurality of microphones from the number of audio noise sources are limited to having real components greater than or equal to zero and less than approximately unity, and imaginary parts between approximately plus and minus 0.1. 16. A system as claimed in claim 2, wherein the one or more variables are updated according to a steepest descent method. 17. A system as claimed in claim 16, wherein a normalised least mean square (NLMS) algorithm is used to limit a step size used in the steepest descent method. 18. A system as claimed in claim 17, wherein the NLMS algorithm comprises a step of estimating the power of the signals received by each of the plurality of microphones, and wherein that step is performed by a 1-tap recursive filter with adjustable time coefficient or weighted windows with adjustable time span which averages the power in each frequency bin. 19. A system as claimed in claim 16, wherein the step size used in the steepest descent method is reduced to a greater extent the greater the ratio of estimated target signal power to the signal power received by one of the plurality of microphones designated as a reference microphone. 20. A system as claimed in claim 2, wherein the phase of the estimated target signal is the phase of one of the plurality of microphones designated as a reference microphone.
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이 특허에 인용된 특허 (17)
Zurek Patrick M. (Arlington MA) Greenberg Julie E. (Farmington Hills MI) Peterson Patrick M. (Cambridge MA), Adaptive beamforming for noise reduction.
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