# US 2014/0153731 A1 · Asymmetric temperature compensation of microphone sensitivity at an active noise reduction system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0153731 A1 - Document ID: US20140153731A1 - Status: Published application - Kind: A1 - Application number: 13/705,432 - Filed: 2012-12-05 - Published: 2014-06-05 - Earliest claimed: 2012-12-05 - Assignees: Bose Corporation - Inventors: Davis Pan - Web page: https://patentgrep.com/patent/US20140153731A1 ## CPC - G10K 11/002: {Devices for damping, suppressing, obstructing or conducting sound in acoustic devices (G10K1/06 - G10K1/10 take precedence; for electro-mechanical transducers for communication H04R3/002)} - G10K 11/17821: {characterised by the analysis of the input signals only} - G10K 11/17833: {by using a self-diagnostic function or a malfunction prevention function, e.g. detecting abnormal output levels} - G10K 11/17854: {the filter being an adaptive filter} - G10K 11/17883: {the reference signal being derived from a machine operating condition, e.g. engine RPM or vehicle speed} - H04R 3/00: Circuits for transducers (arrangements for producing a reverberation or echo sound G10K15/08; amplifiers H03F) - H04R 2410/03: Reduction of intrinsic noise in microphones - 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 - 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 Provided are a method and apparatus comprising an active noise reduction system. The active noise reduction system comprises an input transducer for transducing acoustic noise to a noise signal. The input transducer has a first sensitivity at a threshold temperature. The active noise reduction system includes circuitry that receives the noise signal and, in response, compensates for an effect by an ambient temperature on a second sensitivity of the input transducer by preventing the second sensitivity from being greater than the first sensitivity in response to a temperature deviation from the threshold temperature. ## Claims ### Claim 1 An apparatus, comprising: an active noise reduction system, comprising: an input transducer for transducing acoustic noise to a noise signal, wherein the input transducer has a first sensitivity at a threshold temperature; and circuitry that receives the noise signal and, in response, compensates for an effect by an ambient temperature on a second sensitivity of the input transducer by preventing the second sensitivity from being greater than the first sensitivity in response to a temperature deviation from the threshold temperature. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the circuitry includes a thermistor. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the input transducer includes a microphone. ### Claim 4 (depends on 1) The apparatus of claim 1, wherein the active noise reduction system is a feed-forward active noise reduction system. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the circuitry performs a first temperature compensation operation that rigidly controls the second sensitivity to be at or near the first sensitivity in response to a first temperature deviation between the threshold temperature and an upper temperature limit or a lower temperature limit where a preferred noise cancellation performance is desired. ### Claim 6 (depends on 5) The apparatus of claim 5, wherein the circuitry performs a second temperature compensation operation that controls the second sensitivity less rigidly than the first temperature compensation operation in response to a second temperature deviation where the ambient temperature is greater than the upper temperature limit or less than the lower temperature limit. ### Claim 7 (depends on 5) The apparatus of claim 5, wherein sensitivity loss occurs at a temperature greater than the upper temperature limit or less than the lower temperature limit. ### Claim 8 (depends on 1) The apparatus of claim 1, wherein the circuitry automatically compensates for the effect by the ambient temperature on the second sensitivity of the input transducer by controlling the second sensitivity to be substantially the same as the first sensitivity. ### Claim 9 (depends on 1) The apparatus of claim 1, wherein the threshold temperature is at or about 20° C. ### Claim 10 A sensitivity adjustment circuit, comprising: a sensitivity modification device that automatically compensates for an effect by an ambient temperature on a sensitivity of an input transducer by preventing the sensitivity from being greater than a threshold temperature sensitivity in response to a temperature deviation from a threshold temperature. ### Claim 11 (depends on 10) The sensitivity adjustment circuit of claim 10, wherein the sensitivity modification device includes a thermistor. ### Claim 12 (depends on 10) The sensitivity adjustment circuit of claim 10, wherein the sensitivity modification device performs a first temperature compensation operation that rigidly controls the sensitivity to be at or near the threshold temperature sensitivity in response to a first temperature deviation between the threshold temperature and an upper temperature limit or a lower temperature limit where a preferred noise cancellation performance is desired. ### Claim 13 (depends on 12) The sensitivity adjustment circuit of claim 12, wherein the sensitivity modification device performs a second temperature compensation operation that controls the sensitivity less rigidly than the first temperature compensation operation in response to a second temperature deviation where the ambient temperature is greater than the upper temperature limit or less than the lower temperature limit. ### Claim 14 (depends on 12) The sensitivity adjustment circuit of claim 12, wherein sensitivity loss occurs at a temperature greater than the upper temperature limit or less than the lower temperature limit. ### Claim 15 (depends on 10) The sensitivity adjustment circuit of claim 10, wherein the threshold temperature is at or about 20° C. ### Claim 16 (depends on 10) The sensitivity adjustment circuit of claim 10, wherein the sensitivity modification device automatically compensates for an effect by the ambient temperature on the sensitivity of the input transducer by controlling the sensitivity to be substantially the same as the threshold temperature sensitivity. ### Claim 17 A method for operating an active noise reduction system, comprising: transducing, at an input transducer, acoustic noise to a noise signal, the input transducer has a first sensitivity at a threshold temperature; and compensating for an effect by an ambient temperature on a second sensitivity of the input transducer by preventing the second sensitivity from being greater than the first sensitivity in response to a temperature deviation from the threshold temperature. ### Claim 18 (depends on 17) The method of claim 17, further comprising: performing a first temperature compensation operation that rigidly controls the second sensitivity to be at or near the first sensitivity in response to a first temperature deviation between the threshold temperature and an upper temperature limit or a lower temperature limit where a preferred noise cancellation performance is desired. ### Claim 19 (depends on 18) The method of claim 18, further comprising: performing a second temperature compensation operation that controls the second sensitivity less rigidly than the first temperature compensation operation in response to a second temperature deviation where the ambient temperature is greater than the upper temperature limit or less than the lower temperature limit. ### Claim 20 (depends on 18) The method of claim 18, wherein sensitivity loss occurs at a temperature greater than the upper temperature limit or less than the lower temperature limit. ### Claim 21 (depends on 17) The method of claim 17, further comprising: automatically compensating for an effect by the ambient temperature on the second sensitivity of the input transducer by controlling the second sensitivity to be substantially the same as the first sensitivity. ### Claim 22 (depends on 17) The method of claim 17, wherein the threshold temperature is at or about 20° C.