# US 12,002,445 B2 · Cancel filter coefficient generation method, cancel filter coefficient generation apparatus, and program > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,002,445 B2 - Document ID: US12002445B2 - Status: Granted - Kind: B2 - Application number: 17/918,295 - Filed: 2020-04-16 - Published: 2023-08-31 - Granted: 2024-06-04 - Earliest claimed: 2020-04-16 - Assignees: Nippon Telegraph and Telephone Corporation - Applicants: Nippon Telegraph and Telephone Corporation - Inventors: Kazunori Kobayashi; Masahiro Fukui - Web page: https://patentgrep.com/patent/US12002445B2 ## CPC - G10K 11/17853: {of the filter} - G10K 11/17881: {the reference signal being an acoustic signal, e.g. recorded with a microphone} - G10K 11/17823: {Reference signals, e.g. ambient acoustic environment} - G10K 11/17825: {Error signals} - G10K 11/17827: {Desired external signals, e.g. pass-through audio such as music or speech} - G10K 11/17835: {using detection of abnormal input signals} - G10K 2210/12: Rooms, e.g. ANC inside a room, office, concert hall or automobile cabin - G10K 2210/3016: Control strategies, e.g. energy minimization or intensity measurements - G10K 2210/3025: Determination of spectrum characteristics, e.g. FFT - 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 ## Abstract Provided is a technology for generating an elimination filter coefficient for suppressing degradation of noise elimination performance. An elimination filter coefficient generation method for inputting a reference signal output from a reference microphone for collecting noise and an error signal output from an error microphone for collecting sound at a position that needs to be silent, and generating an elimination filter coefficient used for filtering for generating an elimination signal for eliminating noise at the position that needs to be silent from the reference signal includes: a route filtering step for generating a filtered reference signal from the reference signal by filtering using a route filter coefficient indicating acoustic characteristics of a route from a speaker for emitting sound based on the elimination signal to the error microphone; a first noise signal generation step for generating a predetermined signal as a first noise signal; a noise signal addition step for generating an added reference signal from the filtered reference signal and the first noise signal; and an elimination filter coefficient generation step for generating the elimination filter coefficient from the error signal and the added reference signal. ## Claims ### Claim 1 An elimination filter coefficient generation method in which an elimination filter coefficient generation apparatus inputs a reference signal output from a reference microphone for collecting noise in a predetermined space and an error signal output from an error microphone for collecting sound at a position that needs to be silent and generates an elimination filter coefficient used for filtering for generating an elimination signal for eliminating noise at the position that needs to be silent from the reference signal, the elimination filter coefficient generation method comprising: a route filtering step for generating a filtered reference signal from the reference signal by filtering using a route filter coefficient indicating acoustic characteristics of a route from a speaker for emitting sound based on the elimination signal to the error microphone; a first noise signal generation step for generating a signal having predetermined frequency characteristics and level as a first noise signal; a noise signal addition step for generating an added reference signal from the filtered reference signal and the first noise signal; and an elimination filter coefficient generation step for generating, from the error signal and the added reference signal, as the elimination filter coefficient, an elimination filter coefficient with which a signal exceeding a specification range of the speaker is not generated. ### Claim 2 (depends on 1) The elimination filter coefficient generation method according to claim 1, wherein the first noise signal is a signal that is uncorrelated to the error signal. ### Claim 3 (depends on 1) The elimination filter coefficient generation method according to claim 1, wherein the first noise signal is a signal with which a ratio of a frequency spectral of the first noise signal to a frequency spectral of the filtered reference signal increases in a frequency band where reproduction volume is small in frequency characteristics of the speaker. ### Claim 4 (depends on 1) A non-transitory computer-readable recording medium storing a program for causing a computer to execute the elimination filter coefficient generation method according to claim 1. ### Claim 5 An elimination filter coefficient generation method in which an elimination filter coefficient generation apparatus inputs a reference signal output from a reference microphone for collecting noise in a predetermined space and an error signal output from an error microphone for collecting sound at a position that needs to be silent and generates an elimination filter coefficient used for filtering for generating an elimination signal for eliminating noise at the position that needs to be silent from the reference signal, the elimination filter coefficient generation method comprising: a route filtering step for generating a filtered reference signal from the reference signal by filtering using a route filter coefficient indicating acoustic characteristics of a route from a speaker for emitting sound based on the elimination signal to the error microphone; a reproduction filter coefficient generation step for generating, from the reference signal, a reproduction filter coefficient indicating frequency characteristics of the reference signal; a first noise signal generation step for generating a signal having predetermined frequency characteristics and level as a first noise signal; a reproduction filtering step for generating a filtered first noise signal from the first noise signal by filtering using the reproduction filter coefficient; a noise signal addition step for generating an added reference signal from the filtered reference signal and the filtered first noise signal; and an elimination filter coefficient generation step for generating the elimination filter coefficient from the error signal and the added reference signal. ### Claim 6 (depends on 5) A non-transitory computer-readable recording medium storing a program for causing a computer to execute the elimination filter coefficient generation method according to claim 5. ### Claim 7 An elimination filter coefficient generation method in which an elimination filter coefficient generation apparatus inputs a reference signal output from a reference microphone for collecting noise in a predetermined space and an error signal output from an error microphone for collecting sound at a position that needs to be silent and generates an elimination filter coefficient used for filtering for generating an elimination signal for eliminating noise at the position that needs to be silent from the reference signal, the elimination filter coefficient generation method comprising: a route filtering step for generating a filtered reference signal from the reference signal by filtering using a route filter coefficient indicating acoustic characteristics of a route from a speaker for emitting sound based on the elimination signal to the error microphone; a second noise signal generation step for generating a second noise signal by applying a predetermined gain to the reference signal to add a predetermined delay; a noise signal addition step for generating an added reference signal from the filtered reference signal and the second noise signal; and an elimination filter coefficient generation step for generating the elimination filter coefficient from the error signal and the added reference signal. ### Claim 8 (depends on 5) A non-transitory computer-readable recording medium storing a program for causing a computer to execute the elimination filter coefficient generation method according to claim 5. ### Claim 9 An elimination filter coefficient generation method in which an elimination filter coefficient generation apparatus inputs a reference signal output from a reference microphone for collecting noise in a predetermined space and an error signal output from an error microphone for collecting sound at a position that needs to be silent and generates an elimination filter coefficient used for filtering for generating an elimination signal for eliminating noise at the position that needs to be silent from the reference signal, wherein the elimination filter coefficient has no frequency band having a gain that generates a signal exceeding reproduction capability of a speaker for emitting sound based on the elimination signal. ### Claim 10 (depends on 9) A non-transitory computer-readable recording medium storing a program for causing a computer to execute the elimination filter coefficient generation method according to claim 9. ### Claim 11 An elimination filter coefficient generation apparatus for inputting a reference signal output from a reference microphone for collecting noise in a predetermined space and an error signal output from an error microphone for collecting sound at a position that needs to be silent, and generating an elimination filter coefficient used for filtering for generating an elimination signal for eliminating noise at the position that needs to be silent from the reference signal, the elimination filter coefficient generation apparatus comprising: a route filter for generating a filtered reference signal from the reference signal by filtering using a route filter coefficient indicating acoustic characteristics of a route from a speaker for emitting sound based on the elimination signal to the error microphone; a first noise signal generation circuitry for generating a signal having predetermined frequency characteristics and level as a first noise signal; a noise signal addition circuitry for generating an added reference signal from the filtered reference signal and the first noise signal; and an elimination filter coefficient generation circuitry for generating, from the error signal and the added reference signal, as the elimination filter coefficient, an elimination filter coefficient with which a signal exceeding a specification range of the speaker is not generated.