# US 2025/0097657 A1 · Interpolation of finite impulse response filters for generating sound fields > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2025/0097657 A1 - Document ID: US20250097657A1 - Status: Published application - Kind: A1 - Application number: 18/962,327 - Filed: 2024-11-27 - Published: 2025-03-20 - Earliest claimed: 2022-10-12 - Assignees: Harman International Industries, Incorporated - Applicants: Harman International Industries, Incorporated - Inventors: Alfredo FERNANDEZ FRANCO - Web page: https://patentgrep.com/patent/US20250097657A1 ## CPC - H04S 7/301: {Automatic calibration of stereophonic sound system, e.g. with test microphone} - H04S 7/303: {Tracking of listener position or orientation} - H04R 3/04: for correcting frequency response - H04S: STEREOPHONIC SYSTEMS - 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 Various embodiments disclose a computer-implemented method comprising determining a target location in an environment, determining a set of sub-band impulse responses for a first frequency sub-band, each in the set of sub-band impulse responses being associated with a location proximate to the target location, selecting a first pair of sub-band impulse responses for the first frequency sub-band among pairs within the set of sub-band impulse responses, computing a first coherence value indicating a coherence level between sub-band impulse responses in the first pair, determining that the first coherence value is below a coherence threshold, in response, combining the sub-band impulse responses using a non-linear interpolation technique to generate an estimated impulse response for the first frequency sub-band for the target location, generating, based on the estimated impulse response, a filter for a speaker, filtering an audio signal, and causing the speaker to output the filtered audio signal. ## Claims ### Claim 1 A computer-implemented method comprising: determining a target location in an environment; computing a first coherence value indicating a level of coherence between a first sub-band impulse response and a second sub-band impulse response for a first frequency sub-band, the first and second sub-band impulse responses being associated with corresponding locations that are proximate to the target location; combining the first and second sub-band impulse responses using non-linear interpolation when the first coherence value is below a coherence threshold or using linear interpolation when the first coherence value is equal to or above the coherence threshold to generate an estimated impulse response for the first frequency sub-band for the target location; generating, based at least on the estimated impulse response, a filter for a speaker; filtering, by the filter, an audio signal to generate a filtered audio signal; and causing the speaker to output the filtered audio signal. ### Claim 2 (depends on 1) The computer-implemented method of claim 1, wherein the corresponding locations are within a threshold distance of the target location, and wherein the threshold distance is one of a Euclidean distance or a perceived audio distance. ### Claim 3 (depends on 1) The computer-implemented method of claim 1, wherein the target location is based on a location of a listener within the environment. ### Claim 4 (depends on 1) The computer-implemented method of claim 1, further comprising: determining a second target location in the environment, wherein the second target location corresponds to a second listener within the environment; computing a second coherence value indicating a level of coherence between a third sub-band impulse response and a fourth sub-band impulse response for the first frequency sub-band, the third and fourth sub-band impulse responses being associated with corresponding locations that are proximate to the second target location; combining the third and fourth sub-band impulse responses using non-linear interpolation when the second coherence value is below the coherence threshold or using linear interpolation when the second coherence value is equal to or above the coherence threshold to generate an estimated impulse response for the first frequency sub-band for the second target location; generating, based on the third and fourth sub-band impulse responses, a second estimated impulse response for the second target location; and generating, based at least on the second estimated impulse response, a second filter for the speaker. ### Claim 5 (depends on 1) The computer-implemented method of claim 1, wherein the non-linear interpolation comprises a technique selected from a group consisting of: nearest-neighbor interpolation, a Lagrange interpolation, a least-squares interpolation, a bicubic spline interpolation, a cosine interpolation, or a parabolic interpolation. ### Claim 6 (depends on 1) The computer-implemented method of claim 1, wherein linear interpolation comprises a weighted interpolation. ### Claim 7 (depends on 1) The computer-implemented method of claim 1, further comprising: determining an updated target location in the environment; determining a first updated sub-band impulse response and a second updated sub-band impulse response for the first frequency sub-band, the first updated and second updated sub-band impulse responses being associated with a corresponding location that is proximate to the updated target location; generating an updated estimated impulse response based on the first and second updated sub-band impulse responses; and updating, based on the updated estimated impulse response, the filter for the speaker. ### Claim 8 (depends on 1) The computer-implemented method of claim 1, wherein generating, based at least on the estimated impulse response, the filter for the speaker further comprises modifying at least one of a center frequency, gain, a Q factor, or a cutoff frequency based upon the estimated impulse response. ### Claim 9 (depends on 1) The computer-implemented method of claim 1, wherein generating, based at least on the estimated impulse response, the filter for the speaker further comprises generating one or more digital signal processor (DSP) coefficients for the filter based on the estimated impulse response. ### Claim 10 One or more non-transitory computer-readable media comprising instructions that, when executed by one or more processors, cause the one or more processors to perform the steps of: determining a target location in an environment; computing a first coherence value indicating a level of coherence between a first sub-band impulse response and a second sub-band impulse response for a first frequency sub-band, the first and second sub-band impulse responses being associated with corresponding locations that are proximate to the target location; combining the first and second sub-band impulse responses using non-linear interpolation when the first coherence value is below a coherence threshold or using linear interpolation when the first coherence value is equal to or above the coherence threshold to generate an estimated impulse response for the first frequency sub-band for the target location; generating, based at least on the estimated impulse response, a filter for a speaker; filtering, by the filter, an audio signal to generate a filtered audio signal; and causing the speaker to output the filtered audio signal. ### Claim 11 (depends on 10) The one or more non-transitory computer-readable media of claim 10, wherein the corresponding locations of the first and second sub-band impulse responses is within a threshold distance of the target location, and wherein the threshold distance is one of a Euclidean distance or a perceived audio distance. ### Claim 12 (depends on 10) The one or more non-transitory computer-readable media of claim 10, wherein the target location is based on a location of a listener within the environment. ### Claim 13 (depends on 10) The one or more non-transitory computer-readable media of claim 10, wherein the instructions cause the one or more processors to further perform the steps of: determining a second target location in the environment, wherein the second target location corresponds to a second listener within the environment; computing a second coherence value indicating a level of coherence between a third sub-band impulse response and a fourth sub-band impulse response for the first frequency sub-band, the third and fourth sub-band impulse responses being associated with corresponding locations that are proximate to the second target location; combining the third and fourth sub-band impulse responses using non-linear interpolation when the second coherence value is below the coherence threshold or using linear interpolation when the second coherence value is equal to or above the coherence threshold to generate an estimated impulse response for the first frequency sub-band for the second target location; generating, based on the third and fourth sub-band impulse responses, a second estimated impulse response for the second target location; and generating, based at least on the second estimated impulse response, a second filter for the speaker. ### Claim 14 (depends on 10) The one or more non-transitory computer-readable media of claim 10, wherein the non-linear interpolation comprises a technique selected from a group consisting of: nearest-neighbor interpolation, a Lagrange interpolation, a least-squares interpolation, a bicubic spline interpolation, a cosine interpolation, or a parabolic interpolation. ### Claim 15 (depends on 10) The one or more non-transitory computer-readable media of claim 10, wherein the linear interpolation comprises a weighted interpolation. ### Claim 16 (depends on 10) The one or more non-transitory computer-readable media of claim 10, wherein the instructions cause the one or more processors to further perform the steps of: determining an updated target location in the environment; determining a first updated sub-band impulse response and a second updated sub-band impulse response for the first frequency sub-band, the first updated and second updated sub-band impulse responses being associated with a corresponding location that is proximate to the updated target location; generating an updated estimated impulse response based on the first and second updated sub-band impulse responses; and updating, based on the updated estimated impulse response, the filter for the speaker. ### Claim 17 A system comprising: a memory storing instructions; and a processor coupled to the memory that executes the instructions to perform steps comprising: determining a target location in an environment; computing a first coherence value indicating a level of coherence between a first sub-band impulse response and a second sub-band impulse response for a first frequency sub-band, the first and second sub-band impulse responses being associated with corresponding locations that are proximate to the target location; combining the first and second sub-band impulse responses using non-linear interpolation when the first coherence value is below a coherence threshold or using linear interpolation when the first coherence value is equal to or above the coherence threshold to generate an estimated impulse response for the first frequency sub-band for the target location; generating, based at least on the estimated impulse response, a filter for a speaker; filtering, by the filter, an audio signal to generate a filtered audio signal; and causing the speaker to output the filtered audio signal. ### Claim 18 (depends on 17) The system of claim 17, further comprising a sensor; wherein the steps further comprise: acquiring, using the sensor, sensor data associated within a listener within the environment; and determining the target location based on the sensor data. ### Claim 19 (depends on 17) The system of claim 17, wherein the filter comprises a filter bank including distinct filters for separate frequency bands. ### Claim 20 (depends on 17) The system of claim 17, wherein the steps further comprise: determining an updated target location in the environment; determining a first updated sub-band impulse response and a second updated sub-band impulse response for the first frequency sub-band, the first updated and second updated sub-band impulse responses being associated with a corresponding location that is proximate to the updated target location; generating an updated estimated impulse response based on the first and second updated sub-band impulse responses; and updating, based on the updated estimated impulse response, the filter for the speaker.