[TEP_Kim_Il_Sung]

Erect sandbags around your unit, leaving about 4' or enough for servicing. Make it 2 bags wide, and 4 bags higher than the unit.

This will turn the noise into a slight murmur.

[micro_cam]

It needs good air flow to work well and the noise is only really a problem inside the house in the room next to it. I may put some sound insulation on the wall at some point.

[windexh8er]

Really? I'm curious what brand of heat pumps these are. I have two air source units. One is a whole home Carrier Infinity unit (4 ton) and a GE single head ductless mini-split. The Carrier heats and cools our entire home save for a sunroom that's not ducted which is why we also have the mini-split. I never hear either unit.

[spikej]

There must be a more aesthetically pleasing option...

[OJFord]

As a Briton not used to these things at all, I would think surrounding it in sandbags is the more aesthetically pleasing option.

[jfk13]

As a Briton, I can't help thinking that once the unit is in place, with its double-wall sandbag enclosure (including 4' service space), I won't have any garden left.

[sirmike_]

Why bother building the other three walls? Wouldn’t one SB wall between the unit and the exterior wall of the building cut down the noise enough?

[jfk13]

Well... supposing I did have a bit of garden left, I might like to enjoy it in peace without hearing a constant noise of machinery.