We recently bought a house with two goodman heat pumps (1 1/2 and 2 1/2 tons) where the heat pumps are mounted on angle iron frames bolted to the foundation of the house. This was done because house is on the side of a very steep hill. The noise from the units is very pronounced in heating mode. Other than replacing the units (they are brand new so that's probably out of the question), would it help to install vibration pads underneath the units or a sound blanket (not sure if there is such a thing)?
Any suggestions would be appreciated. One thing to note, when the system is in cooling mode, the noise isn't nearly as loud.