Wearable Audio Device Magnetic Nulling for Earth-Field Detection
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Solution Overview
Problem
Magnetometers in wearable audio devices, such as earbuds, are overwhelmed by the strong magnetic fields from other magnets within the device, preventing accurate detection of the Earth's magnetic field.
Innovation Solution
Incorporating a docking or parking magnet, such as a Halbach array, to partially or fully null the transducer magnetic field at the magnetometer, ensuring it operates within its linear range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the magnetometer is placed close to other magnets in the wearable audio device, then the device size is reduced, but the magnetic field from other magnets overwhelms the magnetometer and prevents it from detecting the Earth's magnetic field accurately
Solution Approach 1:
The patent converts the harmful strong magnetic field from the transducer magnet into a beneficial nulling field by using a second magnet positioned to create a magnetic field that cancels the transducer magnet's field at the magnetometer location. This allows the magnetometer to detect the Earth's magnetic field accurately despite the close proximity of strong magnets, resolving the contradiction between compact device size and measurement precision.
2Measurement precision
If a nulling magnet is added to reduce the transducer magnetic field at the magnetometer, then the magnetometer can detect the Earth's magnetic field accurately, but the device complexity increases
Solution Approach 1:
The patent makes the second magnet serve multiple functions: it acts as a nulling magnet to cancel the transducer magnet's field at the magnetometer location, and simultaneously serves as a docking magnet to magnetically couple the wearable audio device to the charging case. This multi-functionality reduces device complexity by eliminating the need for separate nulling and docking magnets.
3Measurement precision
If the second magnetic field completely nulls the transducer magnetic field at the magnetometer, then the magnetometer can detect the Earth's magnetic field accurately, but the docking or parking functionality is weakened
Solution Approach 1:
The patent creates different magnetic field conditions at different locations: at the magnetometer location, the second magnet's field cancels the transducer magnet's field to enable accurate Earth's magnetic field detection; at the docking interface location, the second magnet's field reinforces or maintains sufficient magnetic attraction for docking functionality. This spatial differentiation of magnetic field properties resolves the contradiction between measurement precision and docking force.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate detection of the Earth's magnetic field by the magnetometer, improving orientation tracking and docking/parking functionality of wearable audio devices.
Implementation Method 1
a docking or parking magnet constructed and arranged to produce a nulling magnetic field that reduces the strength of the transducer magnetic field at the magnetometer
Implementation Method 2
The docking or parking magnet may comprise an array of a plurality of differently magnetized regions. This array may comprise a Halbach array.
Data Source
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AI summary
A wearable audio device, such as an earphone (20), with a magnetic field sensor (72) that is constructed and arranged to sense the Earth's magnetic field. A magnet (38) in the earphone (20), for example the magnet (38) of the electro-acoustic transducer (30), produces a first magnetic field having a first magnetic field strength. A docking or parking magnet (74) in the earphone (20) produces a second magnetic field that is configured to reduce an influence of the first magnetic field on the magnetic field sensor (72).