# US 11,122,357 B2 · Forming virtual microphone arrays using dual omnidirectional microphone array (DOMA) > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,122,357 B2 - Document ID: US11122357B2 - Status: Granted - Kind: B2 - Application number: 13/959,708 - Filed: 2013-08-05 - Published: 2014-07-03 - Granted: 2021-09-14 - Earliest claimed: 2007-06-13 - Assignees: Jawbone Innovations, LLC - Applicants: Jawbone Innovations, LLC - Inventors: Gregory C. Burnett - Web page: https://patentgrep.com/patent/US11122357B2 ## CPC - H04R 1/1091: {Details not provided for in groups H04R1/1008 - H04R1/1083} - G10L 21/0208: Noise filtering - H04R 1/406: {microphones} - H04R 3/002: {Damping circuit arrangements for transducers, e.g. motional feedback circuits} - H04R 3/005: {for combining the signals of two or more microphones (specially adapted for hearing aids H04R25/407)} - H04R 3/04: for correcting frequency response - G10L 2021/02165: {Two microphones, one receiving mainly the noise signal and the other one mainly the speech signal} - H04R 2460/01: Hearing devices using active noise cancellation - 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 dual omnidirectional microphone array noise suppression is described. Compared to conventional arrays and algorithms, which seek to reduce noise by nulling out noise sources, the array of an embodiment is used to form two distinct virtual directional microphones which are configured to have very similar noise responses and very dissimilar speech responses. The only null formed is one used to remove the speech of the user from V2. The two virtual microphones may be paired with an adaptive filter algorithm and VAD algorithm to significantly reduce the noise without distorting the speech, significantly improving the SNR of the desired speech over conventional noise suppression systems. ## Claims ### Claim 1 A device, comprising: a first virtual microphone comprising a first combination of a first microphone signal and a second microphone signal, wherein the first microphone signal is generated by a first physical microphone and the second microphone signal is generated by a second physical microphone; a second virtual microphone comprising a second combination of the first microphone signal and the second microphone signal, wherein the second combination is different from the first combination, wherein the first virtual microphone and the second virtual microphone are distinct virtual directional microphones with substantially similar responses to noise and substantially dissimilar responses to speech; and a signal processor coupled with the first and second microphone signals and operative to combine the first and second microphone signals by filtering and summing in the time domain, to apply a varying linear transfer function between the first and second microphone signals, and to generate an output signal having noise content that is attenuated with respect to speech content. ### Claim 2 (depends on 1) The device of claim 1, wherein the signal processor comprises one or more digital signal processors (DSPs). ### Claim 3 (depends on 1) The device of claim 1, wherein the noise content comprises acoustic noise and the speech content comprises human speech. ### Claim 4 (depends on 1) The device of claim 1, wherein the signal processor is operative to add a delay to the first microphone signals. ### Claim 5 (depends on 4) The device of claim 4, wherein the signal processor is operative to raise the delay to a power that is proportional to a time difference between arrival of the speech at the first virtual microphone and arrival of the speech at the second virtual microphone. ### Claim 6 (depends on 4) The device of claim 4, wherein the signal processor is operative to raise the delay to a power that is proportional to a sampling frequency multiplied by a quantity equal to a third distance subtracted from a fourth distance, the third distance being between the first physical microphone and a speech source of the speech and the fourth distance being between the second physical microphone and the speech source. ### Claim 7 (depends on 1) The device of claim 1, wherein the first and second physical microphones comprise omnidirectional microphones. ### Claim 8 (depends on 1) The device of claim 1, wherein the first and second physical microphones are included in a microphone array. ### Claim 9 (depends on 1) The device of claim 1, wherein the first physical microphone and the second physical microphones are disposed along an axis and are separated from each other by a first distance. ### Claim 10 (depends on 9) The device of claim 9, wherein a midpoint of the axis is a second distance from a speech source that generates the speech, wherein the speech source is located in a direction defined by an angle relative to the midpoint. ### Claim 11 (depends on 10) The device of claim 10, wherein the first virtual microphone is formed by subtracting the second microphone signal from the first microphone signal. ### Claim 12 (depends on 10) The device of claim 10, wherein the second virtual microphone is formed by subtracting the first microphone signal from the second microphone signal. ### Claim 13 (depends on 1) The device of claim 1, wherein the first virtual microphone is formed by subtracting the second microphone signal from a delayed version of the first microphone signal. ### Claim 14 (depends on 1) The device of claim 1, wherein the second virtual microphone is formed by subtracting the first microphone signal from a delayed version of the second microphone signal. ### Claim 15 A device, comprising: a first virtual microphone comprising a first combination of a first microphone signal and a second microphone signal, wherein the first microphone signal is generated by a first physical microphone and the second microphone signal is generated by a second physical microphone; a second virtual microphone comprising a second combination of the first microphone signal and the second microphone signal, wherein the second combination is different from the first combination, wherein the first virtual microphone and the second virtual microphone are distinct virtual directional microphones with substantially similar responses to noise and substantially dissimilar responses to speech; a virtual microphone array including the first and second virtual microphones and having a single null oriented in a direction toward a source of speech; and a signal processor coupled with the first and second microphone signals and operative to combine the first and second microphone signals by filtering and summing in the time domain, to apply a varying linear transfer function between the first and second microphone signals, and to generate an output signal having noise content that is attenuated with respect to speech content. ### Claim 16 (depends on 15) The device of claim 15, wherein the source of speech comprises human speech. ### Claim 17 (depends on 15) The device of claim 15, wherein the second virtual microphone includes a second linear response to speech and the single null comprises a region of the second linear response to speech having a measured response level that is lower than a measured response level of any other region of the second linear response to speech. ### Claim 18 (depends on 15) The device of claim 15, wherein the first virtual microphone is formed by subtracting the second microphone signal from a delayed version of the first microphone signal. ### Claim 19 (depends on 15) The device of claim 15, wherein the second virtual microphone is formed by subtracting the first microphone signal from a delayed version of the second microphone signal. ### Claim 20 (depends on 15) The device of claim 15, wherein the first and second physical microphones are included in a microphone array.