Method of broadband constant directivity beamforming for non linear and non axi-symmetric sensor arrays embedded in an obstacle
First Claim
1. A beamformer for correcting the beam pattern and beamwidth of a microphone array embedded in an obstacle whose shape is not axi-symmetric, comprising:
- a multiplier for multiplying a signal d of a sound source from a directivity angle θ
to each respective microphone of said array by a respective weighting vector w to generate a product that enhances the signal d while minimising noise n, where n is not correlated to the signal d, and where n and d are both dependant upon frequency ω
; and
an adder for summing each respective product to generate an output signal such that woptHd=1;
wherein optimised weighting vector wopt is a solution of
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Abstract
A method is provided for designing a broad band constant directivity beamformer for a non-linear and non-axi-symmetric sensor array embedded in an obstacle having an odd shape, where the shape is imposed by industrial design constraints. In particular, the method of the present invention provides for collecting the beam pattern and keeping the main lobe reasonably constant by combined variation of the main lobe with the look direction angle and frequency. The invention is particularly useful for microphone arrays embedded in telephone sets but can be extended to other types of sensors.
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Citations
15 Claims
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1. A beamformer for correcting the beam pattern and beamwidth of a microphone array embedded in an obstacle whose shape is not axi-symmetric, comprising:
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a multiplier for multiplying a signal d of a sound source from a directivity angle θ
to each respective microphone of said array by a respective weighting vector w to generate a product that enhances the signal d while minimising noise n, where n is not correlated to the signal d, and where n and d are both dependant upon frequency ω
; andan adder for summing each respective product to generate an output signal such that woptHd=1; wherein optimised weighting vector wopt is a solution of - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for correcting the beam pattern and beamwidth of a microphone array embedded in an obstacle whose shape is not axi-symmetric, comprising:
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positioning respective microphones of said array at selected locations on said obstacle such that the distance between microphones is less than one half of λ
/2, where λ
represents wavelength;for each said microphone calculating a weighting vector w such that the Hermitian product woptHd=1 enhances the signal d of a sound source for a given signal angle of arrival θ
while minimising noise n due to the environment, where n is not correlated to the signal d, and where n and d are both dependant upon frequency ω
;wherein optimised weighting vector wopt is a solution of - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A method of designing a broad band constant directivity beamformer for a non-linear and non-axi-symmetric sensor array embedded in an obstacle, comprising:
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applying a numerical method to said obstacle to generate a boundary elements mesh; positioning array sensors at selected nodes of the boundary element mesh for defining sectors all around the array, modelling a set of potential sources to be detected by said sensors in said sectors and determining the acoustic pressure at each of said sensors for each of said sources; defining a noise field characterised by a normalized noise correlation matrix (Rnn) at said array sensors; for each sector, with a look direction θ
, defining (i) a pair of vectors whose directions are symmetric relative to direction θ
, and at least one of (ii) a pair of vectors whose directions are asymmetric relative to direction θ
, and (iii) a single vector with a direction different from θ
, andapplying a set of constraints to said vectors in each sector to obtain an optimal weighting vector wopt for correction of beamwidth and beampattern asymmetry.
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Specification