# US 2021/0176579 A1 · Spatial Audio Parameters and Associated Spatial Audio Playback > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0176579 A1 - Document ID: US20210176579A1 - Status: Published application - Kind: A1 - Application number: 17/045,334 - Filed: 2019-03-28 - Published: 2021-06-10 - Earliest claimed: 2018-04-06 - Assignees: Nokia Technologies Oy - Applicants: Nokia Technologies Oy - Inventors: Mikko-Ville LAITINEN; Juha VILKAMO - Web page: https://patentgrep.com/patent/US20210176579A1 ## CPC - H04S 7/30: {Control circuits for electronic adaptation of the sound field} - G10L 25/21: the extracted parameters being power information - H04R 3/005: {for combining the signals of two or more microphones (specially adapted for hearing aids H04R25/407)} - H04R 5/027: Spatial or constructional arrangements of microphones, e.g. in dummy heads - H04R 5/04: Circuit arrangements, {e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments (combinations of amplifiers H03F3/68; stereophonic systems H04S)} - H04S 3/008: {in which the audio signals are in digital form, i.e. employing more than two discrete digital channels (data reduction aspects thereof based on psychoacoustics G10L19/02)} - H04S 3/02: of the matrix type, i.e. in which input signals are combined algebraically, e.g. after having been phase shifted with respect to each other - G10L 19/008: Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing - G10L 25/06: the extracted parameters being correlation coefficients - H04R 3/12: for distributing signals to two or more loudspeakers {(specially adapted for hearing aids H04R25/407)} - H04S 2400/01: Multi-channel, i.e. more than two input channels, sound reproduction with two speakers wherein the multi-channel information is substantially preserved - H04S 2400/15: Aspects of sound capture and related signal processing for recording or reproduction - H04S 2420/03: Application of parametric coding in stereophonic audio systems - H04S 2420/11: Application of ambisonics in stereophonic audio systems - H04S: STEREOPHONIC SYSTEMS - G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING - 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 An apparatus including at least one processor and at least one memory including a computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: determine, for two or more microphone audio signals, at least one spatial audio parameter for providing spatial audio reproduction; determine at least one coherence parameter associated with a sound field based on the two or more microphone audio signals, such that another sound field is configured to be reproduced based on the at least one spatial audio parameter and the at least one coherence parameter. ## Claims ### Claim 1 An apparatus comprising at least one processor and at least one non-transitory memory including a computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: determine, for two or more microphone audio signals, at least one spatial audio parameter for providing spatial audio reproduction; determine at least one coherence parameter associated with a sound field based on the two or more microphone audio signals, such that another sound field is configured to be reproduced based on the at least one spatial audio parameter and the at least one coherence parameter; and output the at least one coherence parameter. ### Claim 2 (depends on 1) The apparatus as claimed in claim 1, wherein the apparatus caused to determine the at least one coherence parameter is further caused to determine at least one of: at least one spread coherence parameter based on a determination of coherence within the sound field, the at least one spread coherence parameter being associated with a coherence of a directional part of the sound field; or at least one surrounding coherence parameter based on a determination of coherence within the sound field, the at least one surrounding coherence parameter being associated with a coherence of a non-directional part of the sound field. ### Claim 3 (depends on 1) The apparatus as claimed in claim 1, wherein the apparatus caused to determine the at least one spatial audio parameter is further caused to determine at least one of: a direction parameter; an energy ratio parameter; a direct-to-total energy parameter; a directional stability parameter; or an energy parameter. ### Claim 4 (depends on 1) The apparatus as claimed in claim 1, further caused to determine an associated audio signal based on the two or more microphone audio signals, wherein the sound field is reproduced based on the at least one spatial audio parameter, the at least one coherence parameter and the associated audio signal. ### Claim 5 (depends on 1) The apparatus as claimed in claim 1, wherein the apparatus caused to determine at least one coherence parameter based on a determination of coherence within the sound field being further caused to: determine zeroth and first order spherical harmonics based on the two or more microphone audio signals; generate at least one general coherence parameter based on the zeroth and first order spherical harmonics; and generate the at least one coherence parameter based on the at least one general coherence parameter. ### Claim 6 (depends on 1) The apparatus as claimed in claim 1, wherein the apparatus caused to determine zeroth and first order spherical harmonics based on the two or more microphone audio signals, is further caused to one of: determine time domain zeroth and first order spherical harmonics based on the two or more microphone audio signals and convert the time domain zeroth and first order spherical harmonics to time-frequency domain zeroth and first order spherical harmonics; and convert the two or more microphone audio signals into respective two or more time-frequency domain microphone audio signals and generate time-frequency domain zeroth and first order spherical harmonics based on the time-frequency domain microphone audio signals. ### Claim 7 (depends on 5) The apparatus as claimed in claim 5, wherein when the at least one coherence parameter is generated, the apparatus is further caused to generate: at least one spread coherence parameter based on the at least one general coherence parameter and an energy ratio configured to define a relationship between a direct part and an ambient part of the sound field; and at least one surrounding coherence parameter based on the at least one general coherence parameter and an energy ratio configured to define a relationship between a direct part and an ambient part of the of the sound field. ### Claim 8 (depends on 1) The apparatus as claimed in claim 1, wherein when the at least one coherence parameter is determined, the apparatus is caused to: convert the two or more microphone audio signals into respective two or more time-frequency domain microphone audio signals; determine at least one estimate of non-reverberant sound based on the two or more time-frequency domain microphone audio signals; and determine at least one surrounding coherence parameter based on the at least one estimate of non-reverberant sound and an energy ratio configured to define a relationship between a direct part and an ambient part of the sound field. ### Claim 9 (depends on 8) The apparatus as claimed in claim 8, wherein the apparatus caused to determine the at least one coherence parameter, is further caused to: select one of: the at least one surrounding coherence parameter based on the at least one estimate of non-reverberant sound and the energy ratio; or the at least one surrounding coherence parameter based on the at least one general coherence parameter, based on which surrounding coherence parameter is largest. ### Claim 10 (depends on 1) The apparatus as claimed in claim 1, wherein the apparatus caused to determine at least one coherence parameter for two or more frequency bands. ### Claim 11 An apparatus comprising at least one processor and at least one non-transitory memory including a computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: receive at least one audio signal, the at least one audio signal based on two or more microphone audio signals; receive at least one coherence parameter, associated with a sound field based on two or more microphone audio signals; receive at least one spatial audio parameter for providing spatial audio reproduction; and reproduce another sound field based on the at least one audio signal, the at least one spatial audio parameter and the at least one coherence parameter. ### Claim 12 (depends on 11) The apparatus as claimed in claim 11, wherein the apparatus caused to receive the at least one coherence parameter is further caused to receive at least one of: at least one spread coherence parameter for the at least two frequency bands, the at least one spread coherence parameter being associated with a coherence of a directional part of the sound field; or at least one surrounding coherence parameter, the at least one surrounding coherence parameter being associated with a coherence of a non-directional part of the sound field. ### Claim 13 (depends on 12) The apparatus as claimed in claim 12, wherein the at least one spatial audio parameter comprises at least one of: a direction parameter; an energy ratio parameter; a direct-to-total energy parameter; a directional stability parameter; or an energy parameter, and where the apparatus caused to reproduce the another sound field based on the at least one audio signal, the at least one spatial audio parameter and the at least one coherence parameter is further caused to: determine a target covariance matrix from the at least one spatial audio parameter, the at least one coherence parameter and an estimated energy of the at least one audio signal; generate a mixing matrix based on the target covariance matrix and estimated energy of the at least one audio signal; and apply the mixing matrix to the at least one audio signal to generate at least two output spatial audio signals for reproducing the another sound field. ### Claim 14 (depends on 13) The apparatus as claimed in claim 13, wherein the apparatus caused to determine the target covariance matrix is further caused to: determine a total energy parameter based on the energy of the at least one audio signal; determine a direct energy and an ambience energy based on at least one of: the energy ratio parameter; a direct-to-total energy parameter; a directional stability parameter; or an energy parameter; estimate an ambience covariance matrix based on the determined ambience energy and one of the at least one coherence parameters; estimate at least one of: a vector of amplitude panning gains; an Ambisonic panning vector or at least one head related transfer function, based on an output channel configuration and/or the at least one direction parameter; estimate a direct covariance matrix based on the vector of amplitude panning gains, Ambisonic panning vector or the at least one head related transfer function, a determined direct part energy and a further one of the at least one coherence parameters; and generate the target covariance matrix comprising combining the ambience covariance matrix and direct covariance matrix. ### Claim 15 A method comprising: determining, for two or more microphone audio signals, at least one spatial audio parameter for providing spatial audio reproduction; determining at least one coherence parameter associated with a sound field based on the two or more microphone audio signals, such that another sound field is configured to be reproduced based on the at least one spatial audio parameter and the at least one coherence parameter; and outputting the at least one coherence parameter. ### Claim 16 A method comprising: receiving at least one audio signal, the at least one audio signal based on two or more microphone audio signals; receiving at least one coherence parameter, associated with a sound field based on two or more microphone audio signals; receive at least one spatial audio parameter for providing spatial audio reproduction; and reproducing another sound field based on the at least one audio signal, the at least one spatial audio parameter and the at least one coherence parameter. ### Claim at position 17 -20. (canceled) ### Claim 21 (depends on 15) The method as claimed in claim 15, wherein determining the at least one spatial audio parameter further comprises determining, for the two or more microphone audio signals, at least one of: a direction parameter; an energy ratio parameter; a direct-to-total energy parameter; a directional stability parameter; or an energy parameter. ### Claim 22 (depends on 15) The method as claimed in claim 15, wherein determining the at least one coherence parameter comprises at least one of: converting the two or more microphone audio signals into respective two or more time-frequency domain microphone audio signals; determining at least one estimate of non-reverberant sound based on the two or more time-frequency domain microphone audio signals; determining at least one surrounding coherence parameter based on the at least one estimate of non-reverberant sound and an energy ratio configured to define a relationship between a direct part and an ambient part of the sound field; or selecting one of: the at least one surrounding coherence parameter based on the at least one estimate of non-reverberant sound and the energy ratio; or the at least one surrounding coherence parameter based on at least one general coherence parameter, based on which surrounding coherence parameter is largest. ### Claim 23 (depends on 16) The method as claimed in claim 16, wherein the at least one spatial audio parameter comprises at least one of: a direction parameter; an energy ratio parameter; a direct-to-total energy parameter; a directional stability parameter; or an energy parameter, and where the method further comprises reproducing the another sound field, the at least one spatial audio parameter and the at least one coherence parameter for at least one of: determining a target covariance matrix from the at least one spatial audio parameter, the at least one coherence parameter and an estimated energy of the at least one audio signal; generating a mixing matrix based on the target covariance matrix and estimated energy of the at least one audio signal; or applying the mixing matrix to the at least one audio signal for generating at least two output spatial audio signals for reproducing the another sound field. ### Claim 24 (depends on 16) The method as claimed in claim 16, wherein receiving the at least one coherence parameter further comprises at least one of: at least one spread coherence parameter for the at least two frequency bands, the at least one spread coherence parameter being associated with a coherence of a directional part of the sound field; or at least one surrounding coherence parameter, the at least one surrounding coherence parameter being associated with a coherence of a non-directional part of the sound field.