Boring physics question

[JaXanim]

The floor was resonating like a sounding board for the case. The case is vibrating at a similar frequency to the fan's hum. It's acting like the diaphragm of a loudspeaker.

Mounting the case on feet reduced the noise cos you made contact with the case well away from its area of maximum vibrational displacement (near the centre I'd expect).

You could try sticking something heavy (like a piece of thin lead sheet) to the bottom of the case to change its resonance frequency and thereby its transmission of fan hum into the floor.

Cheers,

JaX

[JaXanim]

@Argo

Hmmm...in my experience, ceilings vibrate more than floors. This idea could exacerbate an already serious resonance situation. And what if people live above? Could lead to difficulties.

By all means try some fishing line, but make sure it's low tension/elastic grade. When I tried this with high tension line, the ceiling sounded like the Albert Hall.

So you see, physics needn't be boring! Good luck!

JaX