How to isolate a refrigerator?

Maril555 that A/C unit is most likely sitting on a concrete covered foam platform that HVAC companies use when doing installs. They dig down about 2-3" and through some sand down to work this foam platform down into it and level it. There really should be no transmission of vibration from mthe unit to the house except through the refridgerant lines. It really is de-coupled from the house.
As far as the refidgerator. I would try to have a freind tip the "empty" appliance forward and use one of those "grabbers" you see in some hardware stores for people to reach items on upper shelves, and place the pads under each rear corner. Then lift the front and slide the pads under each front corner. Just a suggestion.

Theo,
thanks for the info. I'm certain now it's the AC unit, that's causing the problem. The noise in the basement is VERY loud. I can put my hand on the wall and feel the vibration.
I tried rubber and cork pads under the AC unit- no difference, noise is still there.
One thing though- it doesn't seem to be level. Could that exacerbate the problem?
I was thinking of putting the unit in a sand box, sitting on the top of the concrete platfom, it's sitting on now.
The other thing is the lines going from AC into the house.
The hole in the wall, the lines go through, is filled with some kind of elastic material, which seems to be dried out.
Do you think the lines can transmit significant amount of vibration?

Electrically I would suggest putting an Audio Prism Quiet Line filter on the fridge outlet. That does help keep the grunge from the fridge off the house line.

As for mechanical isolation I would suggest looking at the same things that you use in an audio system ... sorbothane pucks and such under the culprit, additional bracing in the floorboards and support struts, etc.

PTM,
The noise is strictly mechanical in nature and is coming from the AC unit, located outside of the house, close to the basement wall, where my speakers are

Why don't you just have the condencing unit moved to a new location?
All they have to do is:
1. Pump the system down, close off the service ports and cut the lines.
1a. All freon is pumped into condencer so you do not lose any.
2. Extend the refigeration lines.
3. Move the electrical disconnect or extend the whip from the electrical disconnect if the unit is not moved too far.
3a. Extend thermostat wire.
4. Evacuate the lines to air handler.
5. Open condencers lines.
6. Add freon maybe, could need a half pound if it is moved further than a few feet or if you were low.
I know this sounds like a lot of work but it can be done in about 4 hours, easy.

You could also have a tech come out with the types of pads that WE use to see if it helps. We use differant types and amounts of isolators depending on the load.

This could also be the line set from the condencer to the air handler vibrating. They may not be supported correctly. If that is the case, isolators will not help. Try having someone hold the lines outside, lightly pulling up and or pushing down to see if that minimizes or changes the noise, I do mean lightly. you do not want to crimp the lines.
Email me so we may talk if you are interested.
I do this work for a living. hvac/e = hevac1