Do all toroidal transformers hum?


Help Gurus,

When I put my ear (about 2 inches from the top)to my integrated amplifier, I can hear a faint hum from both the transformers. Can't hear anything when I move my ear away from the amp. Is this normal?
livin_262002
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The reason for the hum is what is called magnetostriction. You can read about it here.

It may also be sensitive to the tightness of the transformer mounting screws, and to the design of the mounting arrangement, which might influence the degree to which the vibrations are amplified or damped by the surrounding structure.

Regards,
-- Al
You may also help by using either coupling or isolating devices under your amp. Although they work on opposing principals I have found both to improve the sound to a surprising degree. I have been using Audio Points from Star Sound but am now using FIM isolation devices [modified] under all components. But there are many others.
Thank You all for the great advices. Just want to make sure that the hum is not going to damage anything (I'm new to this stuff,so please pardon my ignorance). The DK does have covers on it's transformers.