My residential outside AC unit is making a lot of noise on the outside and also transferring noise and vibrations on the wall on the inside by where the unit's lines enter the house. It is a Lennox 13ACD-060-230-01 unit - approx. 5 years old (new with the house). I have had 2 HVAC guys look at it and they have changed out the fan motor, and tried mounts under the unit and it has not improved. The noise gets worse in the heat of the day - we are in North TX and it has been 100+ lately. It sounds to me like the compressor is making most of the noise on the outside - the HVAC guy that replaced the fan motor said it was the fan motor making the noise and it was going out, but that didn't help. The vibration noise on the inside is the bigger issue - it sounds much like the compressor noise. I was told that the lines are probably resting against either the dry wall or studs in the wall and that is the source of the noise on the inside. The best solution the HVAC guy has for that is to reroute the line on the outside of the house and up into the attic to the unit, by-passing the walls. Any better ideas out there?

Could be, fan blade out of balance,if so replace it
Could be the rubber feet that the compressor sits on are gone or worn out,, its one or the other

I had a lot of noise outside and it was simply a hard plastic tube that wrapped around the wires that was rattling. Easy fix, wired it against the grate.
Sounds like your noise is more serious though.

I have the same problem: The AC refrigerant lines coming into my living room wall are vibrating with the compressor frequency and causing the wall to vibrate. The noise is lound enough that I have to turn up the TV volume when the AC is on.

I had the compressor replaced, the system recharged and tuned up, and there iis no change in the compressor lines to wall vibrations.

I imagine that the only way to cure this is to cut away either the interior or external wall coverings to reroute and isolate the lines with special materials.

Does anyone know anything about how to do this? Or a better way?