Over the past few months there has been a loud humming noise coming from inside the wall where the old electric panel box is located off my kitchen. This noise sounds like the motor of a fridge or or ceiling fan. While this sound is not loud enough to be heard all over the house it can certainly be heard on the stair well and in the family room.

My house is about 54 years old and there is another main electric panel in the family room downstairs, no noise coming from this panel or wall. Help!!

I would guess over time something has loosened due to the slight vibration caused by the flow of electricity. This may cause something to be able to vibrate enough to make noise and resonate in the wall. I would suggest checking that all the screws in the panel are tight. Call an electrician to do it if you are not comfortable working around electricity. If there are devices such as switches or receptacles in that wall check them also.