# US 10,482,868 B2 · Multi-channel acoustic echo cancellation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,482,868 B2 - Document ID: US10482868B2 - Status: Granted - Kind: B2 - Application number: 15/718,911 - Filed: 2017-09-28 - Published: 2019-03-28 - Granted: 2019-11-19 - Earliest claimed: 2017-09-28 - Assignees: Sonos, Inc. - Applicants: Sonos, Inc. - Inventors: Saeed Bagheri Sereshki; Romi Kadri - Web page: https://patentgrep.com/patent/US10482868B2 ## CPC - H04M 9/082: {using echo cancellers (echo cancellers per se H04B3/23)} - G06F 3/165: {Management of the audio stream, e.g. setting of volume, audio stream path} - G10K 11/178: by electro-acoustically regenerating the original acoustic waves in anti-phase - G10L 21/0208: Noise filtering - H04B 17/336: Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR] - H04R 27/00: Public address systems (circuits for preventing acoustic reaction H04R3/02; circuits for distributing signals to loudspeakers H04R3/12; {monitoring or testing arrangements for public address systems H04R29/007}; amplifiers H03F) - G10K 2210/3012: Algorithms - G10K 2210/505: Echo cancellation, e.g. multipath-, ghost- or reverberation-cancellation - G10L 2021/02082: {the noise being echo, reverberation of the speech} - H04R 2227/005: Audio distribution systems for home, i.e. multi-room use - H04M: TELEPHONIC COMMUNICATION (circuits for controlling other apparatus via a telephone cable and not involving telephone switching apparatus G08) - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - G10K: SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR - G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING - H04B: TRANSMISSION - 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) ## Abstract A method of operating a playback device includes receiving source audio content that includes a first and second channel stream of audio. The method also includes playing back, via a first and second speaker driver of the playback device, the first and second channel streams of audio, thereby producing a first and second channel audio output. A captured stream of audio is received by a microphone of the playback device, and portions of the captured stream of audio correspond to the first and second channel audio outputs. The first and second channel streams of audio are combined into a compound audio signal, and acoustic echo cancellation is performed on the compound audio signal to produce an acoustic echo cancellation output, which is then applied to the captured stream of audio to increase the signal-to noise ratio of the captured stream of audio. ## Claims ### Claim 1 A method of operating a playback device having a first speaker driver, at least a second speaker driver, and one or more microphones, the method comprising: receiving, via a network interface of the playback device, a source stream of audio comprising source audio content to be played back by the playback device, wherein the source audio content comprises a first channel stream of audio and a second channel stream of audio; producing a first channel audio output by playing back, via the first speaker driver, the first channel stream of audio; producing a second channel audio output by playing back, via the second speaker driver, the second channel stream of audio; receiving, via the one or more microphones, a captured stream of audio comprising a first portion corresponding to the first channel audio output and a second portion corresponding to the second channel audio output, wherein the captured stream of audio has a first signal-to-noise ratio; performing a singular value decomposition on the first channel stream of audio and the second channel stream of audio to result in a combined set of signal components; selecting a subset of the combined set of signal components based on one or more parameters; performing acoustic echo cancellation on the subset of the combined set of signal components, wherein performing acoustic echo cancellation on the subset of the combined set of signal components produces a first acoustic echo cancellation output; and applying the first acoustic echo cancellation output to the captured stream of audio, thereby increasing the signal-to noise ratio of the captured stream of audio from the first signal-to-noise ratio to a second signal-to-noise ratio, wherein the second signal-to-noise ratio is greater than the first signal-to-noise ratio. ### Claim 2 (depends on 1) The method of claim 1, wherein the captured stream of audio comprises a third portion corresponding to a vocal command issued by a user, and wherein applying the first acoustic echo cancellation output to the captured stream of audio, thereby increasing the signal-to-noise ratio of the captured stream of audio from the first signal-to-noise ratio to the second signal-to-noise ratio, results in the first portion and second portion being eliminated or minimized in the captured stream of audio. ### Claim 3 (depends on 1) The method of claim 1, further comprising: transforming both of the subset of the combined set of signal components and the captured stream of audio into a Short-Time Fourier Transform domain. ### Claim 4 (depends on 1) The method of claim 1, wherein selecting the subset of the combined set of signal components based on the one or more parameters comprises selecting a subset of the combined set of signal components having at least one of (a) an energy content above a first threshold energy content or (b) a calculated variance above a first threshold variance. ### Claim 5 (depends on 1) The method of claim 1, wherein the playback device comprises a third speaker driver, wherein the source audio content comprises the first channel stream of audio, the second channel stream of audio, and a third channel stream of audio, and wherein the method further comprises producing a third channel audio output by playing back, via the third speaker driver, the third channel stream of audio. ### Claim 6 (depends on 5) The method of claim 5, wherein performing the singular value decomposition on the first channel stream of audio and the second channel stream of audio to result in the combined set of signal components comprises: performing the singular value decomposition on the first channel stream of audio, the second channel stream of audio, and the third channel stream of audio to result in the combined set of signal components. ### Claim 7 (depends on 1) The method of claim 1, further comprising: detecting a trigger to perform acoustic echo cancellation on the subset of the combined set of signal components, wherein detecting the trigger comprises detecting that (a) a playback function is initiated by the playback device or (b) an unmute command is received by the playback device after the playback function is initiated. ### Claim 8 (depends on 1) The method of claim 1, wherein performing the singular value decomposition on the first channel stream of audio is performed by one or more processors of the playback device, wherein performing the singular value decomposition on the second channel stream of audio is performed by the one or more processors of the playback device, wherein selecting the subset of the combined set of signal components based on the one or more parameters is performed by the one or more processors of the playback device, wherein performing acoustic echo cancellation on the subset of the combined set of signal components is performed by the one or more processors of the playback device, and wherein applying the first acoustic echo cancellation output to the captured stream of audio is performed by the one or more processors of the playback device. ### Claim 9 A tangible, non-transitory computer-readable medium storing instructions that when executed by one or more processors cause a playback device to perform functions comprising: receiving, via a network interface of the playback device, a source stream of audio comprising source audio content to be played back by the playback device, wherein the playback device comprises a first speaker driver and at least a second speaker driver and further comprises one or more microphones, and wherein the source audio content comprises a first channel stream of audio and a second channel stream of audio; producing a first channel audio output by playing back, via the first speaker driver, the first channel stream of audio; producing a second channel audio output by playing back, via the second speaker driver, the second channel stream of audio; receiving, via the one or more microphones, a captured stream of audio comprising a first portion corresponding to the first channel audio output, and further comprising a second portion corresponding to the second channel audio output, wherein the captured stream of audio has a first signal-to-noise ratio; performing a singular value decomposition on the first channel stream of audio and the second channel stream of audio to result in a combined set of signal components; selecting a subset of the combined set of signal components based on one or more parameters; performing acoustic echo cancellation on the subset of the combined set of signal components, wherein performing acoustic echo cancellation on the subset of the combined set of signal components produces a first acoustic echo cancellation output; and applying the first acoustic echo cancellation output to the captured stream of audio, thereby increasing the signal-to noise ratio of the captured stream of audio from the first signal-to-noise ratio to a second signal-to-noise ratio, wherein the second signal-to-noise ratio is greater than the first signal-to-noise ratio. ### Claim 10 (depends on 9) The computer-readable medium of claim 9, wherein the captured stream of audio comprises a third portion corresponding to a vocal command issued by a user, and wherein applying the first acoustic echo cancellation output to the captured stream of audio, thereby increasing the signal-to-noise ratio of the captured stream of audio from the first signal-to-noise ratio to the second signal-to-noise ratio, results in the first portion and second portion being eliminated or minimized in the captured stream of audio. ### Claim 11 (depends on 9) The computer-readable medium of claim 9, further comprising instructions that when executed by the one or more processors cause the playback device to perform functions comprising: transforming both of the subset of the combined set of signal components and the captured stream of audio into a Short-Time Fourier Transform domain. ### Claim 12 (depends on 9) The computer-readable medium of claim 9, wherein selecting the subset of the combined set of signal components based on the one or more parameters comprises selecting a subset of the combined set of signal components having at least one of (a) an energy content above a first threshold energy content or (b) a calculated variance above a first threshold variance. ### Claim 13 (depends on 9) The computer-readable medium of claim 9, wherein the playback device comprises a third speaker driver, wherein the source audio content comprises the first channel stream of audio, the second channel stream of audio, and a third channel stream of audio, and wherein the method further comprises producing a third channel audio output by playing back, via the third speaker driver, the third channel stream of audio. ### Claim 14 (depends on 13) The computer-readable medium of claim 13, wherein performing the singular value decomposition on the first channel stream of audio and the second channel stream of audio to result in the combined set of signal components comprises: performing the singular value decomposition on the first channel stream of audio, the second channel stream of audio, and the third channel stream of audio to result in the combined set of signal components. ### Claim 15 (depends on 9) The computer-readable medium of claim 9, further comprising instructions that when executed by the one or more processors cause the playback device to perform functions comprising: detecting a trigger to perform acoustic echo cancellation on the subset of the first combined set of signal components, wherein detecting the trigger comprises detecting that (a) a playback function is initiated by the playback device or (b) an unmute command is received by the playback device after the playback function is initiated. ### Claim 16 (depends on 9) The computer-readable medium of claim 9, wherein performing the singular value decomposition on the first channel stream of audio is performed by the one or more processors, wherein performing the singular value decomposition on the second channel stream of audio is performed by the one or more processors, wherein selecting the subset of the combined set of signal components based on the one or more parameters is performed by the one or more processors, wherein performing acoustic echo cancellation on the subset of the combined set of signal components is performed by the one or more processors, and wherein applying the first acoustic echo cancellation output to the captured stream of audio is performed by the one or more processors.