[rompic]

See my comment below. The heat pump of my neighbour was perfectly within spec (Fujitsu woha080lfca).

It emitted around 69 dB (measured on our side of the property, also checked by an expert). Allowed (on the border of the property) were 35 dB (rule of thumb: you should not hear it in the surrounding soundscape; note that this is a logarithmic scale so I think it's a factor of 6 or something)

It was especially bad when it had less than 8 degree Celsius because it would defrost every 30 minutes or so.

As I wrote before: location is also an important part: his house is hard walled, ours is a prefab house built out of wood. There are only 4 Meters between our houses, it was approx. 2 meters from our wall blowing in our direction. They only thing they could have made worse is putting it in a corner.

I didn't only hear it, I felt it.

In the end I managed to convince him that I pay an acoustic expert to explain to him that 65 dB is way louder than 35 dB and that putting an acoustic hood around it does not solve the problem (approx -10 db).

[somerandomqaguy]

Was it doing this? https://www.youtube.com/watch?v=wudLk0WoIVo&t=50s

[rompic]

Not that I'm aware off. It's hard to judge because I didn't check a lot of times during the night. What I know though, is that the fan was not blowing up, but sideways into our direction.