# US 10,311,890 B2 · Estimation of background noise in audio signals > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,311,890 B2 - Document ID: US10311890B2 - Status: Granted - Kind: B2 - Application number: 15/782,299 - Filed: 2017-10-12 - Published: 2018-02-01 - Granted: 2019-06-04 - Earliest claimed: 2013-12-19 - Assignees: Telefonaktiebolaget LM Ericsson (publ) - Applicants: Telefonaktiebolaget LM Ericsson (publ) - Inventors: Martin Sehlstedt - Web page: https://patentgrep.com/patent/US10311890B2 ## CPC - G10L 21/0208: Noise filtering - G10L 19/18: Vocoders using multiple modes - G10L 19/24: Variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical encoding or layered encoding - G10L 21/0216: characterised by the method used for estimating noise - G10L 25/06: the extracted parameters being correlation coefficients - G10L 25/21: the extracted parameters being power information - G10L 25/78: Detection of presence or absence of voice signals (switching of direction of transmission by voice frequency in two-way loud-speaking telephone systems H04M9/10) - G10L 25/81: for discriminating voice from music - G10L 25/84: for discriminating voice from noise - H04M 1/62: Constructional arrangements - H04W 8/22: Processing or transfer of terminal data, e.g. status or physical capabilities - G10L 2025/783: {based on threshold decision} - G10L 2025/786: {Adaptive threshold} - G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING - H04M: TELEPHONIC COMMUNICATION (circuits for controlling other apparatus via a telephone cable and not involving telephone switching apparatus G08) - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract The invention relates to a background noise estimator and a method therein, for supporting sound activity detection in an audio signal segment. The method comprises reducing a current background noise estimate when the audio signal segment is determined to comprise music and the current background noise estimate exceeds a minimum value. This is to be performed when an energy level of an audio signal segment is more than a threshold higher than a long term minimum energy level, lt_min, which is determined over a plurality of preceding audio signal segments, or, when the energy level of the audio signal segment is less than a threshold higher than lt_min, but no pause is detected in the audio signal segment. ## Claims ### Claim 1 A method by an apparatus, the method comprising: performing by at least one processor of the apparatus, when an energy level of an audio signal segment is less than a threshold higher than a long term minimum energy level (lt_min) which is determined over a plurality of preceding audio signal segments: reducing a current background noise estimate responsive to a determination that the audio signal segment comprises music and to a determination that the current background noise estimate satisfies a defined rule. ### Claim 2 A method by an apparatus, the method comprising: performing by at least one processor of the apparatus, when an energy level of an audio signal segment is less than a threshold higher than a long term minimum energy level (lt_min) which is determined over a plurality of preceding audio signal segments and no pause is detected in the audio signal segment: reducing a current background noise estimate responsive to a determination that the audio signal segment comprises music and to a determination that the current background noise estimate satisfies a defined rule. ### Claim 3 (depends on 2) The method of claim 2, wherein determining that the current background noise estimate satisfies the defined rule, comprises: determining that the current background noise estimate exceeds a minimum value. ### Claim 4 (depends on 3) The method according to claim 3, wherein the minimum value is greater than zero. ### Claim 5 (depends on 2) The method according to claim 2, further comprising: when the energy level of the audio signal segment is more than the threshold higher than lt_min, reducing the current background noise estimate responsive to the determination that the audio signal segment comprises music and to the determination that the current background noise estimate satisfies the defined rule. ### Claim 6 (depends on 5) The method according to claim 5, wherein when the energy level of the audio signal segment is more than the threshold higher than lt_min is based on information derived from an input audio signal, and is not based on feedback from a sound activity detector. ### Claim 7 (depends on 2) The method according to claim 2, wherein the pause is considered to be detected when one or both of the following is fulfilled: a predefined number of consecutive preceding audio signal segments have been determined not to comprise an active signal; a dynamic of an audio signal comprising the audio signal segment exceeds a signal dynamics threshold. ### Claim 8 (depends on 2) The method according to claim 2, further comprising: altering the audio signal segment by replacing a background noise portion of the audio signal segment with a comfort noise signal based on the reduced background noise estimate. ### Claim 9 (depends on 2) The method according to claim 2, further comprising: receiving the plurality of preceding audio signal segments of the audio signal; calculating lt_min over the plurality of preceding audio signal segments. ### Claim 10 An apparatus comprising: at least one processor configured to perform operations comprising: when an energy level of an audio signal segment is less than a threshold higher than a long term minimum energy level (lt_min) which is determined over a plurality of preceding audio signal segments and no pause is detected in the audio signal segment: reducing a current background noise estimate responsive to a determination that the audio signal segment comprises music and to a determination that the current background noise estimate satisfies a defined rule. ### Claim 11 (depends on 10) The apparatus of claim 10, wherein determining that the current background noise estimate satisfies the defined rule, comprises: determining that the current background noise estimate exceeds a minimum value. ### Claim 12 (depends on 11) The apparatus according to claim 11, wherein the minimum value is greater than zero. ### Claim 13 (depends on 10) The apparatus according to claim 10, further comprising: when the energy level of the audio signal segment is more than the threshold higher than lt_min, reducing the current background noise estimate responsive to the determination that the audio signal segment comprises music and to the determination that the current background noise estimate satisfies the defined rule. ### Claim 14 (depends on 13) The apparatus according to claim 13, wherein when the energy level of the audio signal segment is more than the threshold higher than lt_min is based on information derived from an input audio signal, and is not based on feedback from a sound activity detector. ### Claim 15 (depends on 10) The apparatus according to claim 10, being configured to detect the pause when one or both of the following is fulfilled: a predefined number of consecutive preceding audio signal segments have been determined not to comprise an active signal; a dynamic of an audio signal comprising the audio signal segment exceeds a signal dynamics threshold. ### Claim 16 (depends on 10) The apparatus according to claim 10, wherein the apparatus is a background noise estimator of a Sound Activity Detector. ### Claim 17 (depends on 10) The apparatus according to claim 10, wherein the apparatus is a background noise estimator of a codec. ### Claim 18 (depends on 10) The apparatus according to claim 10, wherein the apparatus is a background noise estimator of a wireless device. ### Claim 19 (depends on 10) The apparatus according to claim 10, wherein the apparatus is a background noise estimator of a network node. ### Claim 20 A computer program product comprising a non-transitory computer readable storage medium storing instructions which, when executed on at least one processor, cause the at least one processor to perform operations comprising: when an energy level of an audio signal segment is less than a threshold higher than a long term minimum energy level (lt_min) which is determined over a plurality of preceding audio signal segments and no pause is detected in the audio signal segment: reducing a current background noise estimate responsive to a determination that the audio signal segment comprises music and to a determination that the current background noise estimate satisfies a defined rule. ### Claim 21 (depends on 20) The computer program product according to claim 20, wherein determining that the current background noise estimate satisfies the defined rule, comprises: determining that the current background noise estimate exceeds a minimum value. ### Claim 22 (depends on 20) The computer program product according to claim 20, wherein the operations further comprise: when the energy level of the audio signal segment is more than the threshold higher than lt_min, reducing the current background noise estimate responsive to the determination that the audio signal segment comprises music and to the determination that the current background noise estimate satisfies the defined rule. ### Claim 23 (depends on 22) The computer program product according to claim 22, wherein when the energy level of the audio signal segment is more than the threshold higher than lt_min is based on information derived from an input audio signal, and is not based on feedback from a sound activity detector. ### Claim 24 (depends on 20) The computer program product according to claim 20, wherein the pause is considered to be detected when one or both of the following is fulfilled: a predefined number of consecutive preceding audio signal segments have been determined not to comprise an active signal; a dynamic of an audio signal comprising the audio signal segment exceeds a signal dynamics threshold.