I have a 10-gallon tank in my bedroom, and in the quiet of the night, I can hear my AquaClear 30's lid vibrating. Removing the lid prevents heat conservation and triggers too much evaporation.
So I stretched a thin rubber band around the back part of the lid's lip:
This suspends the lid a millimeter or two above the filter, yet holds it in place:
No more vibrations!
Enjoy,
Bill