# US 10,313,786 B1 · Beamforming and gainsharing mixing of small circular array of bidirectional microphones > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,313,786 B1 - Document ID: US10313786B1 - Status: Granted - Kind: B1 - Application number: 16/010,774 - Filed: 2018-06-18 - Granted: 2019-06-04 - Earliest claimed: 2018-03-20 - Assignees: Cisco Technology, Inc. - Applicants: Cisco Technology, Inc. - Inventors: Feng Bao; David William Nolan Robison; Tor A. Sundsbarm; Fei Yang - Web page: https://patentgrep.com/patent/US10313786B1 ## CPC - H04R 3/005: {for combining the signals of two or more microphones (specially adapted for hearing aids H04R25/407)} - G10L 21/0232: Processing in the frequency domain - H04R 1/406: {microphones} - G10L 2021/02166: {Microphone arrays; Beamforming} - H04R 2201/401: 2D or 3D arrays of transducers - H04R 2430/23: Direction finding using a sum-delay beam-former - H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K) - G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING ## Abstract A device including an array of bidirectional microphones optimizes the echo rejection of the bidirectional microphones. The microphone array receives audio from an audio source and generates audio signals from each of the bidirectional microphones. The device forms audio beams from combinations of the audio signals generated from the microphone array. Each audio beam captures audio from either its positive polarity zone or its negative polarity zone. The device determines a direction of the audio source and selects a perpendicular audio beam pair based on the direction of the audio source. The perpendicular audio beam pair includes a primary audio beam aimed toward the direction of the audio source and a secondary beam perpendicular to the primary audio beam. The device generates an output signal by combining the primary audio beam with the secondary audio beam based on polarity zone the audio is captured for each audio beam. ## Claims ### Claim 1 A method comprising: at a device including a plurality of bidirectional microphones, receiving audio from an audio source; generating an audio signal from each of the bidirectional microphones; forming a plurality of audio beams from combinations of the audio signals generated from the plurality of bidirectional microphones, wherein each audio beam captures audio from either a respective positive polarity zone or a respective negative polarity zone; determining a direction of the audio source; selecting a perpendicular audio beam pair based on the direction of the audio source, wherein the selected perpendicular audio beam pair includes a primary audio beam aimed toward the direction of the audio source and a secondary audio beam perpendicular to the primary audio beam; and generating an output signal by combining the primary audio beam with the secondary audio beam based on a comparison of which respective polarity zones the audio is captured for the primary audio beam and the secondary audio beam. ### Claim 2 (depends on 1) The method of claim 1, further comprising calculating a signal-to-noise ratio (SNR) of each audio beam, wherein the direction of the audio source is determined based on a comparison of the calculated SNRs of the audio beams. ### Claim 3 (depends on 2) The method of claim 2, wherein selecting the perpendicular audio beam pair further comprises: determining a maximum SNR among the calculated SNRs of the audio beams; and responsive to a determination that the maximum SNR is higher than a previously determined maximum SNR, selecting an audio beam with a minimum SNR as the secondary audio beam and selecting an audio beam perpendicular to the secondary audio beam as the primary audio beam. ### Claim 4 (depends on 3) The method of claim 3, wherein the determination that the maximum SNR is higher than the previously determined maximum SNR includes a determination that the maximum SNR exceeds the previously determined maximum SNR by a first predetermined threshold. ### Claim 5 (depends on 4) The method of claim 4, further comprising: calculating a difference between the maximum SNR and the minimum SNR; comparing the difference to a second predetermined threshold; and selecting the audio beam with the minimum SNR as the secondary audio beam only if the difference is greater than the second predetermined threshold. ### Claim 6 (depends on 5) The method of claim 5, further comprising selecting the audio beam perpendicular to the secondary audio beam as the primary audio beam only if the SNR of the audio beam perpendicular to the secondary audio beam is within a third predetermined threshold of the maximum SNR. ### Claim 7 (depends on 1) The method of claim 1, wherein at least one of the audio beams is formed by combining a first audio signal from a first bidirectional microphone with a time delayed second audio signal from a second bidirectional microphone. ### Claim 8 An apparatus comprising: a plurality of bidirectional microphones, each bidirectional microphone configured to receive audio from an audio source and generate an audio signal; a processor configured to: form a plurality of audio beams from combinations of the audio signals generated from the plurality of bidirectional microphones, wherein each audio beam captures audio from either a respective positive polarity zone or a respective negative polarity zone; determine a direction of the audio source; select a perpendicular audio beam pair based on the direction of the audio source, wherein the selected perpendicular audio beam pair includes a primary audio beam aimed toward the direction of the audio source and a secondary audio beam perpendicular to the primary audio beam; and generate an output signal by combining the primary audio beam with the secondary audio beam based on a comparison of which respective polarity zones the audio is captured for the primary audio beam and the secondary audio beam. ### Claim 9 (depends on 8) The apparatus of claim 8, wherein the processor is further configured to calculate a signal-to-noise ratio (SNR) of each audio beam, and wherein the direction of the audio source is determined based on a comparison of the calculated SNRs of the audio beams. ### Claim 10 (depends on 9) The apparatus of claim 9, wherein the processor is configured to select the perpendicular audio beam pair by: determining a maximum SNR among the calculated SNRs of the audio beams; and responsive to a determination that the maximum SNR is higher than a previously determined maximum SNR, selecting an audio beam with a minimum SNR as the secondary audio beam and selecting an audio beam perpendicular to the secondary audio beam as the primary audio beam. ### Claim 11 (depends on 10) The apparatus of claim 10, wherein the processor is configured to determine that the maximum SNR exceeds the previously determined maximum SNR by a first predetermined threshold. ### Claim 12 (depends on 11) The apparatus of claim 11, wherein the processor is further configured to: calculate a difference between the maximum SNR and the minimum SNR; compare the difference to a second predetermined threshold; and select the audio beam with the minimum SNR as the secondary audio beam only if the difference is greater than the second predetermined threshold. ### Claim 13 (depends on 12) The apparatus of claim 12, wherein the processor is further configured to select the audio beam perpendicular to the secondary audio beam as the primary audio beam only if the SNR of the audio beam perpendicular to the secondary audio beam is within a third predetermined threshold of the maximum SNR. ### Claim 14 (depends on 8) The apparatus of claim 8, wherein the processor is configured to form at least one of the audio beams by combining a first audio signal from a first bidirectional microphone with a time delayed second audio signal from a second bidirectional microphone. ### Claim 15 One or more computer readable storage media encoded with software comprising computer executable instructions and, when the software is executed by a processor, cause the processor to: receive audio of an audio source at a plurality of bidirectional microphones; generate an audio signal from each of the bidirectional microphones; form a plurality of audio beams from combinations of the audio signals generated from the plurality of bidirectional microphones, wherein each audio beam captures audio from either a respective positive polarity zone or a respective negative polarity zone; determine a direction of the audio source; select a perpendicular audio beam pair based on the direction of the audio source, wherein the selected perpendicular audio beam pair includes a primary audio beam aimed toward the direction of the audio source and a secondary audio beam perpendicular to the primary audio beam; generate an output signal by combining the primary audio beam with the secondary audio beam based on a comparison of which respective polarity zones the audio is captured for the primary audio beam and the secondary audio beam. ### Claim 16 (depends on 15) The non-transitory computer readable storage media of claim 15, further comprising instructions operable to cause the processor to calculate a signal-to-noise ratio (SNR) of each audio beam, wherein the direction of the audio source is determined based on a comparison of the calculated SNRs of the audio beams. ### Claim 17 (depends on 16) The non-transitory computer readable storage media of claim 16, further comprising instructions operable to cause the processor to select the perpendicular audio beam pair by: determining a maximum SNR among the calculated SNRs of the audio beams; and responsive to a determination that the maximum SNR is higher than a previously determined maximum SNR, selecting an audio beam with a minimum SNR as the secondary audio beam and selecting an audio beam perpendicular to the secondary audio beam as the primary audio beam. ### Claim 18 (depends on 17) The non-transitory computer readable storage media of claim 17, further comprising instructions operable to cause the processor to determine that the maximum SNR is higher than the previously determined maximum SNR by determining that the maximum SNR exceeds the previously determined maximum SNR by a first predetermined threshold. ### Claim 19 (depends on 18) The non-transitory computer readable storage media of claim 18, further comprising instructions operable to cause the processor to: calculate a difference between the maximum SNR and the minimum SNR; compare the difference to a second predetermined threshold; and select the audio beam with the minimum SNR as the secondary audio beam only if the difference is greater than the second predetermined threshold. ### Claim 20 (depends on 19) The non-transitory computer readable storage media of claim 19, further comprising instructions operable to cause the processor to select the audio beam perpendicular to the secondary audio beam as the primary audio beam only if the SNR of the audio beam perpendicular to the secondary audio beam is within a third predetermined threshold of the maximum SNR.