Heat Pump Noise

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PeterW2

46 posts

Geek

#201322 13-Aug-2016 22:04

Like a previous (now locked) thread I have just read, I, too, am being plagued by the noise of a neighbours heat pump. The unit is a very large one (it's running an indoor ducted unit). This unit makes so much noise (both low frequency hum from the compressor, and fan noise from the two fans) that it prevents me from getting to sleep. When I do eventually get to sleep and I wake up during the night (say for a toilet stop), then it can be a couple of hours before I get back to sleep again. I hear the unit running (during the day) when I'm in the dining room, kitchen, lounge and garage of my house too. I don't think this is OK. I have had the (Auckland) council do noise level readings (and the unit seems to be not as noisy when he's here), but the compliance officer won't come out at night when the unit is running at its loudest. He initially (about two months ago) manage to read a noise power level of 55db at 8:00PM. The owner has fitted some insulation around the compressor and the inside of the casing of the unit, but this has just made the sound deeper - not quieter. The owner was initially OK about moving the unit, but has since expressed his intention of not doing so.

Any advice on how to move forwards please?

Peter W

ArcticSilver

729 posts

Ultimate Geek

#1611215 13-Aug-2016 22:07

Definitely a unfortunate situation. Has the owner tried fitting some form of dampening between the unit and the ground?

Low frequencies are usually vibrations, meaning isolating the unit from the group via some rubber feet may help.

PeterW2

46 posts

Geek

#1611244 13-Aug-2016 22:22

Yes, I have seen rubber under the feet of the unit, although I'm not too sure how effective that would be - given that the unit is 'dynabolted' to the paving stones. I suspect that the dynabolts transmit noise to the paving stones. Although the fan noise definitely appears to be directly radiated from the fans anyway

ArcticSilver

729 posts

Ultimate Geek

#1611245 13-Aug-2016 22:24

PeterW2:

Yes, I have seen rubber under the feet of the unit, although I'm not too sure how effective that would be - given that the unit is 'dynabolted' to the paving stones. I suspect that the dynabolts transmit noise to the paving stones. Although the fan noise definitely appears to be directly radiated from the fans anyway

I know this isn't a great solution, but it may pay to get some specifications on the unit and talk to the manufacturer and noise isolation specialists.

PeterW2

46 posts

Geek

#1611246 13-Aug-2016 22:28

The unit was installed just before last Christmas, and it's been a pain since then - becoming worse during the winter.

I emailed Fujitsu in January, and they basically didn't want to know anything about it, and were unwilling to help. They suggested I contact the council

ArcticSilver

729 posts

Ultimate Geek

#1611254 13-Aug-2016 22:50

PeterW2:

The unit was installed just before last Christmas, and it's been a pain since then - becoming worse during the winter.

I emailed Fujitsu in January, and they basically didn't want to know anything about it, and were unwilling to help. They suggested I contact the council

Do you have a DB meter? Might be worth getting one to get a bit more clout behind your argument with the council.

neb

11294 posts

Uber Geek

Trusted

Lifetime subscriber

#1611607 14-Aug-2016 21:55

ArcticSilver:
I know this isn't a great solution, but it may pay to get some specifications on the unit and talk to the manufacturer and noise isolation specialists.

Actually that's a pretty good solution, because there's often not one single solution available. When it comes to noise issues from the compressor you've potentially got to deal with not just vibration but also the sound of air being pushed around by the fan, even if you have a dead silent fan you're still going to get noise from air movement. Then in terms of dealing with vibration you need to look at isolating the unit from the ground vs.bolting it onto the most solid base you can get (ask audio enthusiasts whether it's better to have your speakers isolated from the floor or bolted to it). I've moved a washing machine up onto sorbothane pads and had vibration get vastly worse because it wasn't being absorbed by the structure of the house any more. OTOH my compressor is bolted onto a massive concrete slab cast into deep clay which does a really good job of dealing with vibrations, the biggest noise you hear is the sound of air moving across the fan and the grille.

aucklander

477 posts

Ultimate Geek

#1618455 27-Aug-2016 20:21

I wouldn't waste time or resources in identifying if the unit is installed correctly or not (rubber feet, etc) or to make measurements.

Let the right people to deal with this. Call Noise Control. It is free of charge, and they have the proper instruments.

On a different note, various councils might have different allowable limits for noise levels at boundary and these limits would vary depending on the area where the property is located, time of day or even day of the week! There might be solutions available, like relocating the outdoor unit (definitely not preferred by the owner), or measures to mitigate the noise (like replacing the fence with a concrete block wall). If you can agree with the neighbor to have the fence replaced by concrete wall this should resolve most of the issue. How wide or how high... that would be for an acoustic consultant to decide, based on the degree of attenuation you require but I feel that min 2m High x 3-4m Wide would be a good start.

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PeterW2

46 posts

Geek

#1618482 27-Aug-2016 20:41

Thank you for your post 'Mastergeek'

I have already spoken to the owner of the house about him moving the unit. He was initially very accepting of doing so, but then dug his toes in - 'due to the holes that would be left behind'. I even offered to pay the costs of moving the unit and re-instating his house, but that didn't seem to sway his decision. My 'research' (internet) suggests that a block wall may well be quite effective at blocking the noise, as a block wall is quite a solid mass, and is therefore more likely to effectively attenuate the low frequency of the compressor. However, a 2 metre high wall won't go up as high as the eves of their house, and I wonder how much of the noise is being reflected off his house. I hear the noise from my bedroom, which is about 20 metres away at the other end of my house, so the noise is travelling some distance. As it's low frequency noise (as well as fan noise), the low frequency noise is more difficult to block out.

I have written to the council for further advice, but I have yet to receive a reply

Peter W

aucklander

477 posts

Ultimate Geek

#1618498 27-Aug-2016 21:28

please post an update when you a reply from Council, if possible, it would be very interesting their take on this.

regarding the wall height - imagine the AC unit is a light source, all the wall needs to do is to cast a shadow over your bedroom, house, affected area, etc.; This wall is heavy, and will not allow noise to be transmitted through it. But will reflect a lot of it back. Attenuation (actual dissipation of the noise wave) needs to be done with specific materials lining the wall facing the noise source to reduce the intensity of the "reflected" wave. There are such materials which are suitable for outdoor installation, I can look it up if you want. I do not remember the name right now, but it was specified in a project I came across, to line the concrete walls surrounding some Chillers, and the only reason for the walls was the noise level at boundary.

PeterW2

46 posts

Geek

#1618506 27-Aug-2016 21:54

Sorry, I replied to 'Master Geek' earlier - I should have said 'Ultimate Geek'.

I will indeed post the council's reply. I have had the 'Environmental Compliance Officer' here to measure the noise levels in the past but, unfortunately, the noise wasn't loud on the last 2 or 3 times he came, as the unit 'amps' up and down during the course of the night.

Yes, I understand the noise being like light. I can hear the hum though a big part of my house, so I am unsure whether this noise is radiated noise or transmitted through 'conduction'. I am assuming that most of it is radiated (even I am unsure if I'm even using the right terminology here). I have read about acoustic walls being built of 'special' materials. However, the point is - I am hearing the noise, it's extremely irritating, and I don't feel that I should be the one who should cop (all) the cost of making it quiet at my home.

Peter W