# US 8,571,226 B2 · Automatic polarity adaptation for ambient noise cancellation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,571,226 B2 - Document ID: US8571226B2 - Status: Granted - Kind: B2 - Application number: 12/964,859 - Filed: 2010-12-10 - Published: 2012-06-14 - Granted: 2013-10-29 - Earliest claimed: 2010-12-10 - Assignees: Sony Corporation; Sony Mobile Communications Inc. - Applicants: Peter Isberg - Inventors: Peter Isberg - Web page: https://patentgrep.com/patent/US8571226B2 ## CPC - G10K 11/17875: {using an error signal without a reference signal, e.g. pure feedback} - G10K 11/17825: {Error signals} - G10K 11/1783: {handling or detecting of non-standard events or conditions, e.g. changing operating modes under specific operating conditions} - G10K 11/17854: {the filter being an adaptive filter} - G10K 11/17857: {Geometric disposition, e.g. placement of microphones} - G10K 11/17885: {additionally using a desired external signal, e.g. pass-through audio such as music or speech} - G10K 2210/1081: Earphones, e.g. for telephones, ear protectors or headsets - G10K 2210/3016: Control strategies, e.g. energy minimization or intensity measurements - 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 A sound reproducing device has a loudspeaker arranged to produce sound from an audio signal provided by an audio signal source. A microphone is positioned to pick up ambient noise and generate a microphone signal which comprises the noise. An ambient noise cancellation (ANC) system receives the microphone signal from the microphone and generates anti-noise corresponding to the ambient noise in the microphone signal. An automatic polarity adaptation (AAP) system monitors the ANC system and, when a decision criterion is fulfilled, causes a switch in polarity for the generated anti-noise. ## Claims ### Claim 1 A sound reproducing device having: a loudspeaker arranged to produce sound from an audio signal provided by an audio signal source; a microphone positioned to pick up ambient noise and generate a microphone signal comprising said noise; an ambient noise cancellation (ANC) system arranged to receive the microphone signal from said microphone and to generate anti-noise corresponding to the ambient noise in said microphone signal; and an automatic polarity adaptation (AAP) system arranged to monitor said ANC system and, when a decision criterion is fulfilled, to cause a switch in polarity for the generated anti-noise, wherein the generated anti-noise is added to said audio signal provided by said audio signal source to form a resulting audio signal which is fed to said loudspeaker, and wherein said AAP system is arranged to cause said switch in polarity for the generated anti-noise by reversing the polarity of said resulting audio signal; said AAP system comprising: control means coupled to monitor said ANC system; switch means coupled to be controllable by said control means and having an output coupled to said loudspeaker; and inverter means coupled to receive said resulting audio signal and having an output coupled to an input of said switch means, wherein the control means is arranged, when said decision criterion is fulfilled, to issue a command or control signal to said switch means to enable said switch means to reverse the polarity of said resulting audio signal and deliver it to said loudspeaker. ### Claim 2 (depends on 1) A sound reproducing device as defined in claim 1, said AAP system being arranged to monitor said ANC system by monitoring said microphone signal, wherein said decision criterion is that the sum of the ambient noise and the generated anti-noise in said microphone signal exceeds a predetermined limit. ### Claim 3 (depends on 1) A sound reproducing device as defined in claim 1, said ANC system comprising at least one signal filter and being arranged to perform a feedback loop adaptation process in which filter parameters of said signal filter are adapted in order to minimize the sum of the ambient noise and the generated anti-noise in said microphone signal, wherein said decision criterion is that the feedback loop adaptation process does not converge as expected. ### Claim 4 (depends on 1) A sound reproducing device as defined in claim 1, wherein the AAP system is further arranged, when said decision criterion is fulfilled, to store information in a memory, said stored information indicating that the loudspeaker is mounted with a reversed polarity which requires a switch in polarity for the generated anti-noise in order for said ANC system to work properly. ### Claim 5 (depends on 4) A sound reproducing device as defined in claim 4, wherein at least one of said AAP system or said ANC system is further arranged to use the information stored in said memory in the future for causing said switch in polarity based on said stored information. ### Claim 6 (depends on 1) A portable communication apparatus, comprising a sound reproducing device as defined in claim 1. ### Claim 7 An ambient noise cancellation method, involving: picking up ambient noise to generate a microphone signal; providing ambient noise cancellation (ANC) to generate anti-noise corresponding to the ambient noise in said microphone signal; monitoring the ambient noise cancellation; determining that a decision criterion is fulfilled; and causing a switch in polarity for the generated anti-noise, wherein the generated anti-noise is added to an audio signal provided by an audio signal source to form a resulting audio signal which is fed to a loudspeaker, and wherein said switch in polarity for the generated anti-noise reverses the polarity of said resulting audio signal; the causing the switch in polarity for the generated anti-noise including: monitoring said anti-noise cancellation; when said decision criterion is fulfilled, issuing a command or control signal to enable the reversing of the polarity of said resulting audio signal; and delivering the resulting audio signal to said loudspeaker.