In-ear active noise reduction earphone
First Claim
1. An active noise reduction (ANR) earphone system comprising:
- a feedback microphone for detecting noise;
feedback circuitry, responsive to the feedback microphone, for applying a digital filter Kfb to an output of the feedback microphone to produce an antinoise signal;
an electroacoustic driver for transducing the antinoise signal into acoustic energy;
a housing supporting the feedback microphone and the driver near the entrance to the ear canal; and
an ear tip for coupling the housing to the external anatomical structures of a first ear of a user and positioning the housing to provide a consistent acoustic coupling of the feedback microphone and the driver to the ear canal of the first ear;
wherein the acoustic coupling includes a tube of air defined by the combination of the housing and ear tip, having a length L and effective cross-sectional area A such that the ratio L/A is less than 0.6 mm−
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1 Assignment
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Accused Products
Abstract
An active noise reduction (ANR) earphone system includes a feedback microphone for detecting noise, feedback circuitry, responsive to the feedback microphone, for applying a digital filter Kfb to an output of the feedback microphone to produce an antinoise signal, an electroacoustic driver for transducing the antinoise signal into acoustic energy, a housing supporting the feedback microphone and the driver near the entrance to the ear canal, and an ear tip for coupling the housing to the external anatomical structures of a first ear of a user and positioning the housing to provide a consistent acoustic coupling of the feedback microphone and the driver to the ear canal of the first ear. The acoustic coupling includes a tube of air defined by the combination of the housing and ear tip, having a length L and effective cross-sectional area A such that the ratio L/A is less than 0.6 m−1.
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Citations
18 Claims
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1. An active noise reduction (ANR) earphone system comprising:
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a feedback microphone for detecting noise; feedback circuitry, responsive to the feedback microphone, for applying a digital filter Kfb to an output of the feedback microphone to produce an antinoise signal; an electroacoustic driver for transducing the antinoise signal into acoustic energy; a housing supporting the feedback microphone and the driver near the entrance to the ear canal; and an ear tip for coupling the housing to the external anatomical structures of a first ear of a user and positioning the housing to provide a consistent acoustic coupling of the feedback microphone and the driver to the ear canal of the first ear; wherein the acoustic coupling includes a tube of air defined by the combination of the housing and ear tip, having a length L and effective cross-sectional area A such that the ratio L/A is less than 0.6 mm−
1. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of configuring a feedback filter Kfb for use in an earphone having a feedback-based noise cancellation circuit, the method comprising:
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in a first processor, causing an electroacoustic driver of the earphone to output a calibration signal; receiving an output signal from a microphone acoustically coupled to the driver while the calibration signal is being output; computing a response of the earphone Gds based on the calibration signal and the microphone output signal; computing a target filter having a response Kloop/Gds and determining filter coefficients that will cause Kfb to have such a response; and providing the determined coefficients to a signal processor of the noise cancellation circuit. - View Dependent Claims (14, 15, 16)
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17. An active noise reduction (ANR) earphone system comprising:
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a feedback microphone for detecting noise; digital feedback circuitry, responsive to the feedback microphone, for applying a filter to an output of the feedback microphone to produce an antinoise signal; an electroacoustic driver for transducing the antinoise signal into acoustic energy; a housing supporting the feedback microphone and the driver and maintaining the feedback microphone in a fixed position relative to the driver; a positioning and retaining structure for physically coupling the housing to the outer ear of the user; and an ear tip for acoustically coupling the feedback microphone and the driver to an ear canal of the user; wherein the ear tip and the ear canal form a front chamber containing the feedback microphone and bounded entirely by an interior surface of the ear tip, an interior surface of the ear canal, the user'"'"'s ear drum, and a radiating surface of the driver, and a tube of air between the radiating surface of the driver and the ear canal bounded by the ear tip has a ratio of length L to effective area A no greater than 0.6 mm−
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18. An active noise reduction (ANR) earphone system comprising:
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a feedback microphone for detecting noise; feedback circuitry, responsive to the feedback microphone, for applying a digital filter to an output of the feedback microphone to produce an antinoise signal; an electroacoustic driver for transducing the antinoise signal into acoustic energy; a housing supporting the feedback microphone and the driver and maintaining the feedback microphone in a fixed position relative to the driver; a positioning and retaining structure for coupling the housing to the outer ear of the user; and an ear tip for coupling the feedback microphone and the driver to an ear canal of the user; wherein a front shell of the housing, the ear tip, and the ear canal form a front chamber containing the feedback microphone and bounded by an interior surface of the front shell, an interior surface of the ear tip, an interior surface of the ear canal, the user'"'"'s ear drum, and a radiating surface of the driver, and the interior surface of the ear tip makes up at least twenty percent of the bounding surface of the front chamber not including the interior surface ear canal.
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Specification