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March 28

Magnet affecting resonance.

My teen grandson has a home-craft steel anvil, about 15lbs in weight. When he taps it with a hammer it resonates with a high note for about 3 seconds. However he discovered that when he attached a small but strong magnet to the anvil the resonance is shortened to about 1 second - audibly obvious.
Can someone kindly explain why that should be. Thank you. Richard Avery (talk) 07:27, 28 March 2024 (UTC)[reply]

Surely the same thing would happen if any mass were added to the anvil. Strike tone is somewhat relevant here. I doubt the fact that it is a magnet is relevant. Shantavira|^{feed me} 09:34, 28 March 2024 (UTC)[reply]

An interesting reference, but the magnet is small, about 1 inch long and ovoid, with a minute surface contact with the anvil. But I take your point and perhaps some further experimentation is needed. Thank you. Richard Avery (talk) 10:55, 28 March 2024 (UTC)[reply]

(edit conflict) An effect easily demonstrated by a teaspoon and coffee cup or mug. Taking the handle as 000°, gently tap at 090°, 135° and 180° and you'll hear three different notes. The reason is the mass of the handle lowers the note when it is at an anti-node, but of course has no effect at a node. Martin of Sheffield (talk) 11:14, 28 March 2024 (UTC)[reply]

The magnet turns a high note lasting 3 seconds into an unspecified note lasting one second. It appears that adding the magnet increased the damping of the vibration. Where the magnet touches the anvil, there can be sliding action, leading to dissipation of energy. The same happens if there's a crack in the anvil. In solid metal, there's only elastic deformation, which dissipates no energy. The magnet may also cause dissipation through eddy currents. PiusImpavidus (talk) 11:54, 28 March 2024 (UTC)[reply]

Thank you for the responses, magnetism has little to do with it. A damping effect is at play. Richard Avery (talk) 15:43, 28 March 2024 (UTC)[reply]