A2A Heat pump - External unit sound dispersion

[Ducky]

Hi all,

I was wondering if someone could help me with a question about the sound dispersion of an A2A heat pump. I acknowledge that this might be a slightly "scientific" question, but I thought I would try my luck .

I live in a flat and am putting together a detailed permission request to my buildings freeholder for the installation of an air-to-air heat pump (A2AHP) for my living room. The permission is mainly for the external units, and I need to reassure them and my neighbours that the sound will not be a nuisance.

I've mentioned that the external units will be an entire 6.2 meters away from my neighbours closest balcony door, it will be inside an enclosure and there will be plants, planters and a balcony partition in-between to dampen the sound, and they will only be for our living room, not our bedroom, so they won’t be on during sleeping hours. And they will mainly be used during the winter, so their balcony doors are likely to be shut.

I also want to provide some information and reassurances regarding the actual sound level. If you look at the specs below, it states that for heating the sound power level is 64dB, and the sound pressure level is 51dB. The difference between the sound pressure and power is substantial, so I was wondering which of the two I should use as an indicator of the sound?

Also, if the sound pressure level is 51dB (assuming that sound pressure is what I can use), then what would it be at my neighbours balcony door, which is 6.2 meters away?

Any help would be much appreciated.

Thanks,
Ducky

 

[stem]

Recalling a another distant life when I worked with Rootes Blowers, AFAIK Sound Power is the noise that the unit emits at source. i.e. if you were stood right next to it. This is the usual figure quoted.

Sound Pressure I recall, relates to the general area in which it is located in that the measurement is taken further away and takes into account the acoustic environment in which the device is located, so this figure can change according to location. The Puzzle here (for me) is that I don't see how they can quote a fixed figure in a specification when it's variable. Perhaps someone else might know. The second footnote will have some significance, but I'm not sure what exactly.

it will be inside an enclosure and there will be plants, planters and a balcony partition in-between to dampen the sound

If you are referring to the enclosure that the heat pump comes in with the grilles to allow airflow, that's fine. However, it shouldn't go inside another enclosure or have the grilles obstructed in anyway that would reduce the airflow. Heat pumps work by sucking huge quantities of air through them (˷35m3 a minute from your table above) and extracting the heat out of it before expelling it. If this flow is obstructed in anyway, or the air is not being taken from the outside ambient air it will have a serious effect on its operation.

 

[Ducky]

Thanks @stem. Much appreciated.