Post by wanderer
Has the control box been installed on a wooden partition wall, by any
chance? If so that could be acting like a sounding board. Best bet then
would be to get the installers back and put a suitable fibre board
underneath to dampen the sound.
IME very few electrical devices produce a disturbing amount of hum on
their own. It is normally due to them being mounted on something that is
acting as a sounding board.
You should be able to feel this :- put your fingertips on the wall next
to the box, if it's vibrating then this is likely to be your problem.
If you now push on the wall, does the sound reduce?
If it does then your problem is the wall acting as a sounding board. If
it doesn't then I'm about to waffle a load of irrelevant crap. Also bear
in mind that I've never had this exact problem, but many years ago I
used to design speaker cabinates so I know a bit about acoustics and
Assuming you can't move the box much there are two basic approaches.
1) Changing the way the box is mounted so that the vibrations are not
transferred. Putting soft rubber washers in everywhere you can may help,
but they will need to be quite thick.
2) Stop the board from resonating at the annoying frequency. Anything
you can do to make the panel heavier in one place, lighter in one place,
stiffer, more flexible, larger, smaller, in short any way you can change
the physical properties of the panel will alter the acoustic properties
and may well reduce the resonance - or make it worse!
Taking a wild stab in the dark, but is it mounted on a panel on the
outside of your cupboard under the stairs? If so then putting some sort
of bar across near the centre of the board on which it is mounted may
well significantly reduce the resonance, I say near the centre
deliberately, avoid putting it at the exact centre. You can probably
mount it on the back out of harm's way.
By far the best solution though is to mount it on something that will
not resonate at any annoying frequency.