# US 9,438,996 B2 · Systems and methods for calibrating speakers > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,438,996 B2 - Document ID: US9438996B2 - Status: Granted - Kind: B2 - Application number: 13/773,483 - Filed: 2013-02-21 - Published: 2013-08-22 - Granted: 2016-09-06 - Earliest claimed: 2012-02-21 - Assignees: Intertrust Technologies Corporation - Applicants: Intertrust Technologies Corporation - Inventors: David P. Maher; Gilles Boccon-Gibod; Steve Mitchell - Web page: https://patentgrep.com/patent/US9438996B2 ## CPC - H04S 7/301: {Automatic calibration of stereophonic sound system, e.g. with test microphone} - H04R 3/04: for correcting frequency response - H04R 5/02: Spatial or constructional arrangements of loudspeakers - H04S 7/302: {Electronic adaptation of stereophonic sound system to listener position or orientation (H04S7/301 takes precedence)} - H04S 7/307: {Frequency adjustment, e.g. tone control (H04S7/301 takes precedence)} - H04R 27/00: Public address systems (circuits for preventing acoustic reaction H04R3/02; circuits for distributing signals to loudspeakers H04R3/12; {monitoring or testing arrangements for public address systems H04R29/007}; amplifiers H03F) - H04R 29/004: {for microphones (H04R29/007 takes precedence)} - H04R 29/007: {for public address systems (public address systems per se H04R27/00)} - H04R 2205/021: Aspects relating to docking-station type assemblies to obtain an acoustical effect, e.g. the type of connection to external loudspeakers or housings, frequency improvement - H04R 2227/003: Digital PA systems using, e.g. LAN or internet - H04R 2227/005: Audio distribution systems for home, i.e. multi-room use - H04R 2499/11: Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's - 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 Systems and method are disclosed for facilitating efficient calibration of filters for correcting room and/or speaker-based distortion and/or binaural imbalances in audio reproduction, and/or for producing three-dimensional sound in stereo system environments. According to some embodiments, using a portable device such as a smartphone or tablet, a user can calibrate speakers by initiating playback of a test signal, detecting playback of the test signal with the portable device's microphone, and repeating this process for a number of speakers and/or device positions (e.g., next to each of the user's ears). A comparison can be made between the test signal and the detected signal, and this can be used to more precisely calibrate rendering of future signals by the speakers. ## Claims ### Claim 1 A method for calibrating speakers for a particular environment, the method comprising: positioning a microphone of a portable device at a location in an environment; initiating first playback by an audio source of a first piece of audio content over a first speaker; initiating second playback by the audio source of a second piece of audio content over a second speaker, wherein the first piece of audio content is different from the second piece of audio content, and in which first playback of the first piece of audio content over the first speaker overlaps, at least in part, with second playback of the second piece of audio content over the second speaker; detecting first playback of the first piece of audio content over the first speaker using the microphone; positioning the microphone at another location in the environment; initiating third playback of a third piece of audio content; detecting third playback of the third piece of audio content from the first speaker using the microphone; based at least in part on the detected first playback of the first piece of audio content and the detected third playback of the third piece of audio content, determining one or more adjustments to be applied to additional audio content before additional audio content playback by the first speaker, wherein determining the one or more adjustments includes: accessing a system information file of the portable device to determine a transfer function of the microphone, and determining the one or more adjustments using the transfer function of the microphone; and applying the one or more adjustments to the additional audio content before it is played by the first speaker. ### Claim 2 (depends on 1) The method of claim 1, in which the step of initiating first playback of the first piece of audio content over the first speaker further comprises subsequently initiating fourth playback of the first piece of audio content over the second speaker. ### Claim 3 (depends on 1) The method of claim 1, in which the location comprises a position proximate to a first ear of a person within the environment. ### Claim 4 (depends on 3) The method of claim 3, in which the other location comprises another position proximate to a second ear of the person. ### Claim 5 (depends on 1) The method of claim 1, in which the first piece of audio content and the third piece of audio content are the same. ### Claim 6 (depends on 1) The method of claim 1, in which the first piece of audio content comprises one or more synchronization patterns. ### Claim 7 (depends on 1) The method of claim 1, in which the portable device comprises a mobile phone or tablet. ### Claim 8 (depends on 1) The method of claim 1, in which determining the one or more adjustments to be applied to the additional audio content comprises performing spectral analysis on the detected first playback of the first piece of audio content and the third piece of audio content. ### Claim 9 (depends on 8) The method of claim 8, further comprising: comparing a frequency response of the detected first playback of the first piece of audio content with an ideal frequency response. ### Claim 10 (depends on 1) The method of claim 1, wherein determining a transfer function of the microphone comprises: retrieving a mobile device identifier from the system information file; and retrieving the transfer function of the microphone from a database of microphone transfer functions using a web service. ### Claim 11 (depends on 1) The method of claim 1, wherein the audio source retrieves the first piece of audio content from a test file and retrieves the third piece of audio content from another test file distinct from the test file. ### Claim 12 A portable device for calibrating speakers for a particular environment, the portable device comprising: a microphone; a processor; and a non-transitory memory storing instructions that when executed by the processor of the portable device cause the portable device to perform operations comprising: providing instructions for positioning the microphone of the portable device at a location in an environment; initiating first playback by an audio source of a first piece of audio content over a first speaker; initiating second playback by the audio source of a second piece of audio content over a second speaker, wherein the first piece of audio content is different from the second piece of audio content, and in which first playback of the first piece of audio content over the first speaker overlaps, at least in part, with second playback of the second piece of audio content over the second speaker; detecting first playback of the first piece of audio content over the first speaker using the microphone; providing instructions for positioning the microphone of the portable device at another location in the environment; initiating third playback of a third piece of audio content; detecting third playback of the third piece of audio content from the first speaker using the microphone; based at least in part on the detected first playback of the first piece of audio content and the detected third playback of the third piece of audio content, determining one or more adjustments to be applied to additional audio content before additional audio content playback by the first speaker, wherein determining the one or more adjustments includes: accessing a system information file of the portable device to determine a transfer function of the microphone, and determining the one or more adjustments using the transfer function of the microphone; and applying the one or more adjustments to the additional audio content before it is played by the first speaker. ### Claim 13 (depends on 12) The portable device of claim 12, in which the first piece of audio content and the third piece of audio content are the same. ### Claim 14 (depends on 12) The portable device of claim 12, in which the first piece of audio content comprises one or more synchronization patterns. ### Claim 15 (depends on 12) The portable device of claim 12, in which the portable device comprises a mobile phone or tablet. ### Claim 16 (depends on 12) The portable device of claim 12, in which determining the one or more adjustments to be applied to the additional audio content comprises performing spectral analysis on the detected first playback of the first piece of audio content and the third piece of audio content. ### Claim 17 (depends on 16) The portable device of claim 16, further comprising: comparing a frequency response of the detected first playback of the first piece of audio content with an ideal frequency response. ### Claim 18 (depends on 12) The portable device of claim 12, wherein determining a transfer function of the microphone comprises: retrieving a mobile device identifier from the system information file; and retrieving the transfer function of the microphone from a database of microphone transfer functions using a web service. ### Claim 19 (depends on 12) The portable device of claim 12, wherein the audio source retrieves the first piece of audio content from a test file and retrieves the third piece of audio content from another test file distinct from the test file. ### Claim 20 A non-transitory memory storing instructions that when executed by a processor of a portable device with a microphone cause the portable device to perform operations comprising: providing instructions for positioning the microphone of the portable device at a location in an environment; initiating first playback by an audio source of a first piece of audio content over a first speaker; initiating second playback by the audio source of a second piece of audio content over a second speaker, wherein the first piece of audio content is different from the second piece of audio content, and in which first playback of the first piece of audio content over the first speaker overlaps, at least in part, with second playback of the second piece of audio content over the second speaker; detecting first playback of the first piece of audio content over the first speaker using the microphone; providing instructions for positioning the microphone of the portable device at another location in the environment; initiating third playback of a third piece of audio content; detecting third playback of the third piece of audio content from the first speaker using the microphone; based at least in part on the detected first playback of the first piece of audio content and the detected third playback of the third piece of audio content, determining one or more adjustments to be applied to additional audio content before additional audio content playback by the first speaker, wherein determining the one or more adjustments includes: accessing a system information file of the portable device to determine a transfer function of the microphone, and determining the one or more adjustments using the transfer function of the microphone; and applying the one or more adjustments to the additional audio content before it is played by the first speaker.