Degaussing

Degaussing is the process of decreasing or eliminating an unwanted magnetic field. It is named after Carl Friedrich Gauss, an early researcher in the field of magnetism. Due to magnetic hysteresis it is generally not possible to reduce a magnetic field completely to zero, so degaussing typically induces a very small "known" field referred to as bias.

Audio degaussing is the process by which small amounts of residual magnetism are removed from an analog magnetic tape head. It is typically considered good procedure to degauss a magnetic tape heads after 10 hours of continuous operation. Also referred to as demagnetizing.