> I had me forgetful, the noise happens after a periodo, ,
as italie mentioned, components themselves which are known to make noise are capacitors (if they are leaking) .. the suction cup on the back of the monitor glass (if loose/dirty/leaking), or the flyback transformer (if getting old/worn out)
perhaps if possible, run the monitor and try to locate where (or what general area) of the monitor the noise is coming from (and look at the capacitors to see if any of them have leaked, or bulged/swelled)...
note: if the noise happens after a 'periodo', most likely one of the parts is bad when it becomes hot...
finally, perhaps ask your question at the forum below, which contains lots of friendly experts: