Devices and methods are disclosed that allow for selective acoustic near-field nulls for microphone arrays. One embodiment may take the form of an electronic device including a speaker and a microphone array. The microphone array may include a first microphone positioned a first distance from the sp
Devices and methods are disclosed that allow for selective acoustic near-field nulls for microphone arrays. One embodiment may take the form of an electronic device including a speaker and a microphone array. The microphone array may include a first microphone positioned a first distance from the speaker and a second microphone positioned a second distance from the speaker. The first and second microphones are configured to receive an acoustic signal. The microphone array further includes a complex vector filter coupled to the second microphone. The complex vector filter is applied to an output signal of the second microphone to generate an acoustic sensitivity pattern for the array that provides an acoustic null at the location of the speaker.
대표청구항▼
1. An electronic device comprising: a speaker; anda microphone array comprising: a first microphone positioned a first distance from the speaker;a second microphone positioned a second distance from the speaker, wherein the first and second microphones are configured to receive an acoustic signal;a
1. An electronic device comprising: a speaker; anda microphone array comprising: a first microphone positioned a first distance from the speaker;a second microphone positioned a second distance from the speaker, wherein the first and second microphones are configured to receive an acoustic signal;a complex vector filter coupled to the second microphone, wherein the complex vector filter is applied to an output signal of the second microphone to generate an acoustic sensitivity pattern for the array that provides an acoustic null at the location of the speaker;a first delay circuit coupled to the second microphone;a first difference circuit coupled to the first delay circuit and the first microphone;a multiplier circuit coupled to the output of the first difference circuit;a second difference circuit coupled to the output of the multiplier circuit;a second delay circuit coupled to the first microphone;a third difference circuit coupled to the second delay circuit and an output of the complex vector filter, wherein the output from the third difference circuit is provided to the second difference circuit; anda beamforming circuit coupled to the output of the second difference circuit, wherein the beamforming circuit is configured to form an acoustic sensitivity pattern for the array by adjusting values for the complex vector filter or the multiplier circuit. 2. The electronic device of claim 1, wherein the complex vector filter comprises a gain factor A to compensate for an amplitude difference between the output signal of the second microphone and an output signal from the first microphone. 3. The electronic device of claim 2, wherein the beamforming circuit is configured to selectively provide a value to the multiplier circuit, wherein the acoustic sensitivity pattern is determined at least in part based upon the provided value. 4. The electronic device of claim 3, wherein the beamforming circuit is configured to selectively provide the gain factor A to the complex vector filter, wherein the acoustic sensitivity pattern is determined at least in part based upon the provided value. 5. The electronic device of claim 3, wherein the beamforming circuit is configured to dynamically change the provided value. 6. The electronic device of claim 2, wherein the gain factor A is fixed. 7. The electronic device of claim 2, wherein the effect of the filter in a far field is described by the equation: Y(ω,θ)=|S(ω)|√{square root over ((A2+1)−2A cos φ)},where S is the acoustic signal, ω is the frequency of the signal, θ is an angle of propagation of the signal, k is a wave number, d is the distance between the first and second microphones, and Φ=kd(1+cos θ). 8. The electronic device of claim 1, wherein the first microphone, second microphone and speaker are coaxial. 9. The electronic device of claim 1, wherein the second microphone is located closer to the speaker than the first microphone. 10. The electronic device of claim 9, wherein the microphone array functions as a unidirectional microphone in a near-field. 11. The electronic device of claim 10, wherein the near-field comprises a distance from the speaker less than 100 mm. 12. The electronic device of claim 10, wherein the microphone array functions as an omnidirectional microphone in a far-field. 13. The electronic device of claim 12, wherein the far-field comprises a distance from the first and second microphones greater than 100 mm. 14. The electronic device of claim 1, wherein the first and second microphones are positioned between approximately 10 and 60 mm apart. 15. The electronic device of claim 14, wherein the first and second microphones are positioned approximately 20 mm apart. 16. The electronic device of claim 14, wherein the speaker is positioned between approximately 10 and 30 mm from the second microphone. 17. A method of operating an electronic device to functionally provide an acoustic near-field unidirectional microphone and a far-field omnidirectional microphone, the method comprising: receiving an acoustical signal at an acoustic transducer array, wherein the acoustic transducer array comprises at least a first and a second microphones;generating a plurality of electrical signals, wherein each microphone of the acoustic transducer array generates an electrical signal;filtering at least one of the electrical signals according to the complex vector such that the output is defined by filtering at least one of the electrical signals according to the complex vector such that the output is defined by Y(ω,θ)=|S(ω)|√{square root over ((A2+1)−2A cos φ)},wherein S is the acoustic signal, ω is the frequency of the signal S, θ is an angle of propagation of the signal S, k is a wave number, d is the distance between a first and second microphones, Φ=kd(1+cos θ), and A is a gain factor,wherein filtering generates an acoustical sensitivity pattern for the acoustical transducer array that provides a near-field null. 18. The method of claim 17 further comprising: delaying the at least one of the electrical signals;subtracting the delayed signal from another signal of the electrical signals to output a difference between the delayed signal and the other signal; andmultiplying the difference by value that determines, at least in part, the shape of the acoustic sensitivity pattern. 19. The method of claim 18 further comprising dynamically adjusting at least one of the gain factor A and the value.
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