# US 10,313,509 B2 · Updating filter coefficients during echo cancellation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,313,509 B2 - Document ID: US10313509B2 - Status: Granted - Kind: B2 - Application number: 15/331,695 - Filed: 2016-10-21 - Published: 2017-02-09 - Granted: 2019-06-04 - Earliest claimed: 2015-05-04 - Assignees: Sorenson IP Holdings, LLC - Applicants: Sorenson IP Holdings, LLC - Inventors: Jacob H. Gunther - Web page: https://patentgrep.com/patent/US10313509B2 ## CPC - H04M 3/002: {Applications of echo suppressors or cancellers in telephonic connections (in two-way loud-speaking telephone systems H04M9/08, echo suppressors or cancellers per se H04B3/20)} - G10L 21/0208: Noise filtering - G10L 25/21: the extracted parameters being power information - H04B 3/237: {using two adaptive filters, e.g. for near end and for end echo cancelling} - H04M 9/082: {using echo cancellers (echo cancellers per se H04B3/23)} - G10L 15/26: Speech to text systems (G10L15/08 takes precedence) - G10L 2021/02082: {the noise being echo, reverberation of the speech} - H04M 1/2475: {for a hearing impaired user} - H04M: TELEPHONIC COMMUNICATION (circuits for controlling other apparatus via a telephone cable and not involving telephone switching apparatus G08) - G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING - H04B: TRANSMISSION ## Abstract Updating filter coefficients during echo cancellation is disclosed. In some embodiments, a communication device may include a processor configured to operate a background filter configured as an adaptive filter, operate a foreground filter configured as a fixed filter; and update the foreground filter with coefficients from the background filter responsive to monitoring a history of both a near-end signal energy and an estimated far-end signal energy for a pre-determined time window in which conditions of each of the near-end signal energy and the estimated far-end signal energy are satisfied. ## Claims ### Claim 1 A communication device, comprising: a microphone configured to capture sound; and a computing system communicatively coupled to the microphone and configured to cause the communication device to perform operations, the operations comprising: operate, during a particular period of time, a background filter configured as an adaptive filter and configured to generate an estimated far-end signal based on: background filter coefficients of the background filter that are updated during the particular period of time, a near-end signal generated by the communication device based on the sound captured by the microphone, and a line-in signal that includes: a far-end signal obtained by the communication device over a network; and an echo signal that includes an echo of the near-end signal; determine that the near-end signal is active during the particular period of time; determine that the far-end signal is inactive during the particular period of time based on the estimated far-end signal; and update foreground filter coefficients of a foreground filter with the background filter coefficients in response to determining that the near-end signal is active during the particular period of time and in response to determining that the far-end signal is inactive during the particular period of time, the foreground filter being configured to generate an echo cancelled signal based on the line-in signal, the near-end signal, and the foreground filter coefficients. ### Claim 2 (depends on 1) The communication device of claim 1, wherein: determining that the near-end signal is active during the particular period of time is based on a first number of times, during the particular period of time, that near-end signal energy of the near-end signal is above a first energy threshold, and determining that the far-end signal is inactive during the particular period of time is based on a second number of times, during the particular period of time, that estimated far-end energy of the estimated far-end signal is below a second energy threshold. ### Claim 3 (depends on 2) The communication device of claim 2, wherein: determining that the near-end signal is active during the particular period of time is in response to the first number of times satisfying a first count threshold, and determining that the far-end signal is inactive during the particular period of time is in response to the second number of times satisfying a second count threshold. ### Claim 4 (depends on 3) The communication device of claim 3, wherein the first count threshold is based on a first fraction of the particular period of time. ### Claim 5 (depends on 3) The communication device of claim 3, wherein the second count threshold is based on a second fraction of the particular period of time. ### Claim 6 (depends on 1) The communication device of claim 1, wherein the background filter is a recursive least squared (RLS) adaptive filter. ### Claim 7 (depends on 6) The communication device of claim 6, wherein the RLS adaptive filter implements an algorithm selected from a group consisting of: a covariance-matrix-based RLS algorithm and its square root versions that use a tapped-delay line parameterization and a matrix inversion lemma; an order-recursive RLS algorithm that uses a lattice structure for filter parameterization and error computation; and a fast fixed-order RLS algorithm. ### Claim 8 (depends on 6) The communication device of claim 6, wherein the operations further comprise: operate a state machine to control the RLS adaptive filter and to update the foreground filter with coefficients from the background filter. ### Claim 9 (depends on 8) The communication device of claim 8, wherein the state machine controls an amplitude control block of the near-end signal after updating of the foreground filter coefficients has been initiated. ### Claim 10 A method for cancelling echo, the method comprising: monitoring, during a particular period of time, near-end signal energy of a near-end signal generated by a communication device based on sound captured by a microphone of the communication device; monitoring, during the particular period of time, an estimated far-end signal energy of an estimated far-end signal that is an output of a background filter in which the output is based on the near-end signal and in which the estimated far-end signal is an estimate of a far-end signal obtained by the communication device from a far-end device during a communication session; determining, based on the monitoring of the near-end signal energy, that the near-end signal is active during the particular period of time; determining, based on the monitoring of the estimated far-end signal energy, that the far-end signal is inactive during the particular period of time; updating foreground filter coefficients of a foreground filter with background filter coefficients of the background filter in response to determining that the near-end signal is active during the particular period of time and in response to determining that the far-end signal is inactive during the particular period of time; and performing, by the foreground filter, an echo cancellation on an input signal that includes the far-end signal and an echo signal that includes an echo of the near-end signal. ### Claim 11 (depends on 10) The method of claim 10, wherein determining that the near-end signal is active during the particular period of time is based on a first number of times, during the particular period of time, that the near-end signal energy satisfies a relationship criterion with respect to a first energy threshold. ### Claim 12 (depends on 11) The method of claim 11, wherein determining that the near-end signal is active during the particular period of time is in response to the first number of times satisfying a first count threshold value. ### Claim 13 (depends on 12) The method of claim 12, wherein the first count threshold value is based on a first fraction of the particular period of time. ### Claim 14 (depends on 12) The method of claim 12, wherein the first number of times that the near-end signal energy satisfies the relationship criterion with respect to the first energy threshold is a number of samples of the near-end signal energy that are above the first energy threshold during the particular period of time, and determining that the near-end signal is active during the particular period of time is in response to the first number of times being greater than the first count threshold value. ### Claim 15 (depends on 12) The method of claim 12, wherein the first number of times that the near-end signal energy satisfies the relationship criterion with respect to the first energy threshold is a number of samples of the near-end signal energy that are below the first energy threshold during the particular period of time, and determining that the near-end signal is active during the particular period of time is in response to the first number of times being less than the first count threshold value. ### Claim 16 (depends on 10) The method of claim 10, wherein determining that the far-end signal is inactive during the particular period of time is based on a second number of times, during the particular period of time, that the estimated far-end signal energy satisfies a relationship criterion with respect to a second energy threshold. ### Claim 17 (depends on 16) The method of claim 16, wherein the second number of times that the estimated far-end signal energy satisfies the relationship criterion with respect to the second energy threshold is how many times during the particular period of time that the estimated far-end signal energy is below the second energy threshold. ### Claim 18 (depends on 16) The method of claim 16, wherein the second number of times that the estimated far-end signal energy satisfies the relationship criterion with respect to the second energy threshold is how many times during the particular period of time that the estimated far-end signal energy is above the second energy threshold. ### Claim 19 One or more non-transitory computer-readable media configured to store instructions that, in response to being executed by a processor, cause a communication device to perform operations, the operations comprising: determine that a near-end signal is active during a particular period of time, the near-end signal being generated by a communication device based on sound captured by a microphone of the communication device; determine that a far-end signal is inactive during the particular period of time based on an estimated far-end signal that is an output of a background filter in which the output is based on the near-end signal and in which the estimated far-end signal is an estimate of the far-end signal, which is obtained by the communication device over a network; update foreground filter coefficients of a foreground filter with background filter coefficients of the background filter in response to determining that the near-end signal is active during the particular period of time and in response to determining that the far-end signal is inactive during the particular period of time; and perform, by the foreground filter, an echo cancellation on an input signal that includes the far-end signal and an echo signal that includes an echo of the near-end signal. ### Claim 20 (depends on 19) The one or more non-transitory computer-readable media of claim 19, wherein: determining that the near-end signal is active during the particular period of time is based on a first number of times, during the particular period of time, that near-end signal energy of the near-end signal is on one side of a first energy threshold; and determining that the far-end signal is inactive during the particular period of time is based on a second number of times, during the particular period of time, that estimated far-end signal energy of the estimated far-end signal is on one side of a second energy threshold.