Barkhausen Effect

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Barkhausen Effect Wikipedia.org
Bark.pdf Intalec.com
Listening to Magnetism
"In 1919, Heinrich Barkhausen discovered that magnetizing a metal like iron is not a continuous process, but occurs in tiny jumps, which can be heard if a coil is placed around the metal and connected to an amplifier and a speaker.
The clicks sound like a Geiger counter, and are generated as tiny areas in the metal (called magnetic domains) suddenly merge together.
The equipment needed to hear these sounds is quite simple:
What you need
  • A bolt — 2.5 inches long and 0.25 inches in diameter.
  • Two washers, and a nut that fits the bolt.
  • 60 feet of 22 gauge enamel coated magnet wire.
  • An amplifier — a stereo will work, or a tape recorder, or a sound card, but I used a cheap Radio Shack amplified speaker.
  • A cable with a plug to match your amplifier.
  • A strong magnet. I used one of our 12 millimeter cube super magnets. Weaker magnets might work, but I haven't tried them.

Demonstration Videos

18 second video
Dramatic portrayal of the variation in magnetizable verses permeable ferrous material by the sound of the Barkhausen Effect pulses. The last material tested is non-ferrous "copper".


See also

Scalar Wave Detectors
Some suggest the Barkhausen Effect is sensitive to scalar field gradient change.