I wouldn't worry to be honest. When the pump would be at it loudest (when it's cold) people will not have their windows open. We actually find the water pump is louder than the heat pump and we do get a low hum when it's silent in the house. We never hear the pump.

@batalto thanks for the response. I realise in my original post I got a sentence the wrong way round. I meant "most of the replies seem to be subjective, rather than objective". I have spoken to some people who are not bothered by the sound with their setup, and some who are very disturbed. As I said in the original post, I have a friend who is disturbed by his, and his sleep is measurably affected, as are his neighbours. He is thinking of having it removed if he can't somehow reduce the sound. He is in a urban environment, and also has a larger pump, so is more likely to have issues than someone with a small pump in a house in the middle of a field. I visited another couple with two Nibes and they never hear them, but have very thick stone walls, great glazing and no neighbours, and not near any bedrooms and are happy.

I also visited someone else with a Nibe F2040 16KW and was suprised how loud it was. I measured 65db at one metre and 55db at 5 metres. That was on a iphone, so is not calibrated, however the background noise outside my house about 48db and I can hear that through some of my shut windows, so that gives me some indication.

One issue with anecdotes is that the same make/range varies considerably with output. For example the Nibe F2040 6KW is 50db, and the 16KW is 61db, and if I understand the db scale (which is unlikely!), that means one is 8 times louder than the other at source. In this way, it is easy to see that one person could say that they love the Nibe F2040, and the other says they hate it, depending on what model.

Regarding your comment about people having their windows closed at the coldest time, I agree. However, the people with the Nibe 16KW suggest they can hear it through the wall/ double glazed window when no window is open. Theirs is on the side of a house pointing out onto a field. It doesn't bother them much, but if this were in the side return of a terrace house, this would seem much louder.

My point is really that I have lots of anecdotal evidence either way, and I know that the rated noise of the heat pump only at some parts of its operational range. Overall the picture is still a bit merky. I hope to find a way to resolve this. Knowing the maximum sound power of the heat pumps would really help. A graph of noise vs temperature delta would be fantastic, if only they would publish this.

@olly they do have these, the issue you'll come across is that sound volume very much depends on context settings e.g. where the pump is. Ours is next to a hedge on one side, which absorbs the sound. If it was surrounded by all hard surfaces it would probably be louder.

The sheet in my signature has a sound approval calculator. Maybe that might be a good place for you to start?

To add, another thing is the sensitivity of the occupants.  I specifically chose a larger double-fan heat pump because it was quieter (60dB) than a smaller one with single fans (63dB). The only place next to the house for it to go was beside the kitchen. This means you're about 1m away from it when making a cup of tea.  That was a risk we took since there was not really anywhere else to put it.  The heat pump isn't so bad when you are several metres away, but the noise is still noticeable and it makes the kitchen pretty unpleasant when it's buzzing away.

Also the 'you don't run it when the windows are open' is a fallacy, because we need ventilation - if your windows have trickle vents then you have some part of the window open where sound can get through. Most people don't have a MVHR system to prevent this.

One other knob I tried is 'night mode', which can drop the fan speed to (at most) 50% when you push a button (or timer or relay contact). This doesn't make the slightest bit of difference. I'm exploring if this is due to other issues with the installation. (It was also super noisy to begin with due to air in the pipes, which has gone away as I keep topping up the water)

A family member is autistic and can't abide the noise even at what I'd call barely audible volume, despite their room being two rooms away from the heat pump. We have to turn the whole thing off at night. So we're looking at moving it down the bottom of the garden, which will put it 15m away from the house. It'll make our efficiency worse and require substantial construction works, but you gotta do what you gotta do...

Posted by: @batalto

@olly they do have these

I am having trouble finding any kind of graphs related to noise. The installer manuals have some more information. For example for the aroTherm installation manual quotes some figures on page 94.

If you look at the figures a couple of things are clear:

1) Input air is 7c for all figures. No lower temperatues are quoted, so clearly this is not maximum sound pressure

2) Noise reduction mode figures aren't quoted for for water temperatures above 35c. Does this mean that noise reduction mode can't produce enough heat with flow temperatures with a delta greater than 28c? If so, this is a big limitation. For hot water supplies and radiator systems this might mean this feature is useless.

I found even less information for the Mitsubishu Ecodan. Do you have examples of other manufacters that give the full dataset of sound information?

Regarding the spreadsheet for commissioning that you had in your footer, it was indeed interesting. Thanks for that. The issue remains that if the published sound pressure levels are not the maximum sound pressure levels, then it doesn't really answer the question of whether it will produce acceptable sound levels. It would no doubt help with planning permission/permitted development, as I am sure that they take the sound pressure on the appliance label, not maximum sound pressure.

@prunus you have a point about trickle vents. Yours is another case where I feel full sound pressure information would help, rather than just an appliance rating at A7/W55. Have you ever measured your unit to see if it is in line with the calculations done during the planning phase?

I am also sorry it has caused so much inconvience to you. Whilst I think there is lots to say about sound sensitivity of different people, the accoustic environment that the unit is installed in, etc, the point I really want to pickup on this thread is that I feel the rated sound pressure levels are not representative of the units for the full range of operation. If anyone has empirical measurements which could confirm that on at least one unit, that would help.

@olly 

Hi,

You can find more detailed noise data in the attached documents. The access code for the Midea document is midea2020.

Wow @derek-m, I see graphs. Thanks! The frequency curves are interesting. However, even with the extra info, the same problem remains for the Midea as all measurements are at air 7c, but the unit is measured for heating performance down to Air -20c to water 55c, which gives a delta of 75c across the compressor, rather than the sound measurement taken with only a 48c delta. Now, I appreciate that at -20c it is ok to have excessive noise, as it is pretty rare, but many winter nights are just below zero in the UK, so the measurement is not really a clear indicator of noise. From the PDF:

@olly 

Hi,

I think the only data that you will find on the internet will be no more detailed that that provided.

I suggest that you contact the technical help departments of the various manufacturers to see if they can provide any further data, or at least that they can confirm the power level at which the readings were taken.