# US 10,375,493 B2 · Audio test mode > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,375,493 B2 - Document ID: US10375493B2 - Status: Granted - Kind: B2 - Application number: 16/009,638 - Filed: 2018-06-15 - Published: 2018-12-20 - Granted: 2019-08-06 - Earliest claimed: 2017-06-19 - Assignees: Cirrus Logic, Inc. - Applicants: Cirrus Logic International Semiconductor Ltd. - Inventors: John Paul Lesso; Yanto Suryono - Web page: https://patentgrep.com/patent/US10375493B2 ## CPC - H04R 29/001: {for loudspeakers (H04R29/007 takes precedence)} - G01R 31/3167: Testing of combined analog and digital circuits {(testing ADC's H03M1/1071)} - G10L 19/12: the excitation function being a code excitation, e.g. in code excited linear prediction [CELP] vocoders - H04R 3/04: for correcting frequency response - H04R 29/00: Monitoring arrangements; Testing arrangements {(for hearing aids H04R25/30; detection of loudspeaker connection H04R5/04; sound-field adaptation dependent on speaker detection H04S7/308)} - G01R 31/2825: {in household appliances or professional audio/video equipment (testing LAN's H04L43/50; testing TV systems H04N17/00; testing loudspeakers H04R29/00)} - G10L 19/04: using predictive techniques - H04R 2430/03: Synergistic effects of band splitting and sub-band processing - 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) - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING ## Abstract An audio system receives an input signal and, if the input signal has a sparse representation in the frequency domain, comprising components at at least one frequency of interest, the input signal is filtered in at least one band pass filter, such that only components at the or each frequency of interest are passed to an output. The operation is able in some case to analyze the input signal to determine whether the input signal has a sparse representation in the frequency domain. ## Claims ### Claim 1 An audio system, comprising: an input for receiving an input signal; an output; a sparsity detector for determining whether the input signal has a sparse representation in the frequency domain; a switch, wherein the switch is controlled by an output signal from the sparsity detector based on a determination whether the input signal has a sparse representation in the frequency domain; and a filter for filtering the input signal in at least one band pass filter, wherein, if the input signal is determined to have a sparse representation in the frequency domain, the switch is controlled such that the output of the filter is passed to the output and therefore only components at at least one frequency of interest are passed to the output, and if the input signal is determined not to have a sparse representation in the frequency domain, the switch is controlled such that the input signal is passed to the output. ### Claim 2 (depends on 1) An audio system as claimed in claim 1, configured for analysing the input signal to determine whether the input signal has a sparse representation in the frequency domain. ### Claim 3 (depends on 2) An audio system as claimed in claim 2, configured for determining whether the input signal has a sparse representation in the frequency domain by passing the input signal to a Linear Predictive Coding block. ### Claim 4 (depends on 3) An audio system as claimed in claim 3, configured for determining that the input signal has a sparse representation in the frequency domain if the Linear Predictive Coding block is able to identify one or more frequency component of the input signal, and subtracting the identified one or more frequency component from the input signal produces a result that is below a threshold. ### Claim 5 (depends on 2) An audio system as claimed in claim 2, configured for determining whether the input signal has a sparse representation in the frequency domain by: passing the input signal to a Fast Fourier Transform block; and determining a number of significant frequency components in an output of the Fast Fourier Transform block. ### Claim 6 (depends on 5) An audio system as claimed in claim 5, further configured for: if it is determined that the input signal has a sparse representation in the frequency domain, passing the output signal of the Fast Fourier Transform block to an Inverse Sparse Fourier Transform block to generate an output signal in the time domain comprising only the significant frequency components. ### Claim 7 (depends on 2) An audio system as claimed in claim 2, configured for determining whether the input signal has a sparse representation in the frequency domain by: passing the input signal to a series of one or more notch filters, each having a respective notch filter frequency; determining if an output of any notch filter is below a threshold; and determining that the input signal has a sparse representation in the frequency domain if an output of one notch filter is below a threshold. ### Claim 8 (depends on 7) An audio system as claimed in claim 7, further configured for, if it is determined that the input signal has a sparse representation in the frequency domain: setting a pass band frequency of said at least one band pass filter to be equal to a respective notch filter frequency of a notch filter. ### Claim 9 (depends on 1) An audio system as claimed in claim 1, configured for: analysing the input signal to determine how many significant frequency components are present in the input signal. ### Claim 10 (depends on 9) An audio system as claimed in claim 9, comprising at least one band pass filter, and configured for: adapting the band pass filter to set a number of pass band frequencies thereof based on the determined number of significant frequency components present in the input signal. ### Claim 11 (depends on 1) A device comprising a system as claimed in claim 1, wherein the device comprises a mobile telephone, an audio player, a video player, a mobile computing platform, a games device, a remote controller device, a toy, a machine, or a home automation controller or a domestic appliance. ### Claim 12 A method of operation of an audio system, comprising: receiving an input signal; determining by means of a processing element whether the input signal has a sparse representation in the frequency domain, comprising components at at least one frequency of interest; if the input signal is determined to have a sparse representation in the frequency domain, filtering the input signal in at least one band pass filter, such that only components at the or each frequency of interest are passed to an output; and if the input signal is determined not to have a sparse representation in the frequency domain, passing the input signal to the output. ### Claim 13 (depends on 12) A method as claimed in claim 12, comprising: analysing the input signal to determine whether the input signal has a sparse representation in the frequency domain. ### Claim 14 (depends on 12) A method as claimed in claim 12, comprising: analysing the input signal to determine how many significant frequency components are present in the input signal. ### Claim 15 (depends on 14) A method as claimed in claim 14, comprising: adapting a band pass filter to set a number of pass band frequencies thereof based on the determined number of significant frequency components present in the input signal. ### Claim 16 (depends on 12) A method as claimed in claim 12, comprising determining whether the input signal has a sparse representation in the frequency domain by passing the input signal to a Linear Predictive Coding block, and further comprising: determining that the input signal has a sparse representation in the frequency domain if the Linear Predictive Coding block is able to identify one or more frequency component of the input signal, and subtracting the identified one or more frequency component from the input signal produces a result that is below a threshold. ### Claim 17 (depends on 12) A method as claimed in claim 12, comprising determining whether the input signal has a sparse representation in the frequency domain by: passing the input signal to a Fast Fourier Transform block; and determining a number of significant frequency components in an output of the Fast Fourier Transform block, and further comprising: if it is determined that the input signal has a sparse representation in the frequency domain, passing the output signal of the Fast Fourier Transform block to an Inverse Sparse Fourier Transform block to generate an output signal in the time domain comprising only the significant frequency components. ### Claim 18 (depends on 12) A method as claimed in claim 12, comprising determining whether the input signal has a sparse representation in the frequency domain by: passing the input signal to a series of one or more notch filters, each having a respective notch filter frequency; determining if an output of any notch filter is below a threshold; and determining that the input signal has a sparse representation in the frequency domain if an output of one notch filter is below a threshold, and further comprising, if it is determined that the input signal has a sparse representation in the frequency domain: setting a pass band frequency of said at least one band pass filter to be equal to a respective notch filter frequency of a notch filter. ### Claim 19 (depends on 12) A method as claimed in claim 12, wherein the input signal is considered to have a sparse representation in the frequency domain if the signal contains fewer than five frequency components at significant levels. ### Claim 20 (depends on 12) A non-transitory computer readable storage medium having computer-executable instructions stored thereon that, when executed by processor circuitry, cause the processor circuitry to perform a method according to claim 12.