US Patent 10212507 Headphone

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, a housing constructed and arranged to be positioned at an ear of a wearer so as to direct the audio output at the ear canal of the ear, a magnetic field sensor positioned in the housing and constructed and arranged to sense the Earth's magnetic field, and a nulling magnet positioned in the housing and constructed and arranged to produce a nulling magnetic field that reduces the strength of the transducer magnetic field at the magnetic field sensor.