US Patent 10516929 Audio device

A headphone includes an electro-acoustic transducer for creating audio output, the electro-acoustic transducer comprising a transducer magnet that produces a transducer magnetic field having a magnetic field strength, structure that is constructed and arranged to be positioned so as to direct the audio output at the ear canal of the ear of a wearer of the headphone, a magnetic field sensor constructed and arranged to sense the Earth's magnetic field, and a nulling magnet constructed and arranged to produce a nulling magnetic field that reduces the strength of the transducer magnetic field at the magnetic field sensor.