A ferrite clamp, or ferrite choke, is a device used to reduce the amount of RF (radio frequency) noise, or interference, in a wire that conducts electricity. Ferrite clamps are typically used to improve the performance of sound systems, including microphones.
Ferrite is name given to ceramics formed from various metal oxides. Oxides of iron, manganese, manganese and zinc and nickel and zinc are the most common forms of ferrite.
Ferrite clamps usually consist of a two halves of ferrite that are, literally, clamped around a conducting wire. Ferrite is a highly permeable material and provides less resistance to the flow of magnetic flux in the conductor than air alone, so a ferrite clamps effectively absorbs some of the noise in the wire.
Ferrite may be a highly permeable, but it is also very fragile. Ferrite clamps must therefore be protected against physical damage.