acoustic dampening for a builtin tall freezer housing

[sandyman44]

hi
I have a newly professionally fitted kitchen, one unit is a tall builtin freezer unit. we originally put an AEG freezer in it, but it was incredibly noisy, we were convinced it was dodgy, so it has just been swapped for a Liebherr, and the noise is still there. The noise is NOT the usual crack/whine/pop that people grumble about with modern freezers. Having changed the freezer means that we can't say that the previous freezer was the specific reason behind the issue...

the noise is a constant hum somewhere between 50 and 100hz, audible through the downstairs (up to 2 rooms away from kitchen) . in some specific places you can actually feel the low frequency air vibrations to a very disturbing level in the ears & stomach (like standing next to a nightclub level bass unit) , particularly in one hallway where I assume the dimensions must match the wavelength and so getting a very strong standing wave.

I am pretty sure that the initial generator of the noise is one of the motors of the freezer (proably the frost-free circulation fan), but it is being heavily amplified by the freezer housing - the housing is behaving as a massive sound box, its resonant frequency must be close to that of the motor . putting an ear or hand against the housing/furniture door. I can feel a slight vibration. if I push really hard against the housing/ door, I can stop the vibration/amplification and the noise drops to a practically inaudible level. The kitchen fitting guys are coming to see what they can do, but I would like to seek advice from anyone who's been here before.. has anyone ever come across this before?
I have an engineering degree so I know what laws of physics we are up against , we either need change the resonant frequency of the cabinet or damp it, are there any products that people can recommend / know would work well to provide a damping/isolation around the freezer into the cabinet?

any help appreciated
Ian

 

[foxhole]

Rubber mat under it, it should be the only place it is in contact with a surface to transmit the sound vibrations.

 

[Steve]

A built in fridge freezer sits on the bottom of a cabinet housing. The acoustic contact area here is minimal. One thing I think that helps mine is that it actually sits on 3 layers of chipboard screwed together to make it the right level. The cabinet doesn't normally have a back panel. The top is usually attached somehow at the front, again the contact area is minimal.

One thing I would do is check down either side of the appliance. Check that it is not in contact with the chipboard sides of the cabinet. Also check the shelf above the appliance has space below it. The only contact should be the feet and the top fixing. And the doors of course.