Heart rate sensor and method for measuring a heart rate

A heart rate sensor for determining a heart rate, comprising:

• an in-ear device comprising:
• an in-ear portion configured to contact an ear canal of an user wherein the in-ear portion comprises a distal portion made from a flexible material such that the distal portion moves, e.g. changes shape, in response to a deformation or vibration of the ear canal when the in-ear portion is placed in the ear canal;
• a magnet;
• a magnetic sensor for measuring a change in magnetic flux density caused by movement of the magnet relative to the magnetic sensor;
• and
• a processor connected to the magnetic sensor for receiving a signal representing the measured change in magnetic flux density;
• wherein either the magnet or the magnetic sensor is provided in the distal portion such that a movement of the distal portion resulting from a movement or vibration of the ear canal causes a change in the magnetic flux density measured by the magnetic sensor,
• wherein the processor is configured to:
• determine a movement of the magnet relative to the magnetic sensor based on the measured change in magnetic flux density;
• determine a heart rate of the user, e.g. by first determining a heart beat waveform of the user, based on the determined movement of the magnet relative to the magnetic sensor;
• and
• output a signal representing the determined heart rate of the user.