I am looking into simulating Air-Source heat pump sound with an overlay on background noises - with a setting for load factor and distance.
Do you have any ideas or inspirations on how to solve this issue?
This would help me on simulating the right placement and also whether it makes sense to oversize it a bi in order to have lower sound volumes over the year?
A couple of things that may help.
Ours is as loud as a tumble dryer so we used that as a guide to tell how annoying it would be. I know that’s why less scientific than what you are trying to achieve.
Ours is also over-sized and it rarely runs efficiently because it can’t modulate low enough.
I’ll be honest and say that I’m actually glad it’s oversized and that it cycles because it runs about 10-15 minutes per hour much of the shoulder months so we don’t care about a bit of noise (even from the circulating pumps) because it’s not on much of the time. It’s why I like the revised algorithms I created.
This is a graph with the “average outdoor temp for the day” on the x-axis which shows how the original controller keeps the system running a lot more of the time.
PS having a solar PV diverter also means that much of the time in the Summer (when we’re using the garden) the heat pump doesn’t kick in (such as today).
If you want to know what it might sound like, find a similar one or the same model and record it. Using a mobile phone app, measure the sound level noting very carefully the distance and direction and then play back the recording adjusting the volume so as to get the same sound level at the same distance. The last bit is crucial because of the inverse square law - and beware reflecting surfaces and standing waves, because those will confuse matters significantly. You’ll probably need quite a powerful amplifier/speaker combination to get the same sound pressure level as the real thing.
I tried with my bluetooth speakers - looked for air conditionning sound on spotify / youtube and played it on a phone. on my other phone I installed a dB-Meter-App and set the volume of the aircon noise in order to measure 68 dB (=max sound volume according to the manufacturer’s sound calculator online, not the EU label sound level which is calculated at 35 % load) directly at the surface of the speaker (phone microphone at the bottom). I then placed the speaker at the future site of the heat pump and walked back to my window.
The sound vanished after 3m because of the background sounds (cars and birds) and I am now confident my neighbours will have absolutely no issue with the HP sound.
Does this approach make sense to you?
The approach is sensible, it will give you an indication but it relies heavily on the calibration of the app and your phone. Bear in mind that a change of 10 dB in voltage is very roughly the difference between normal and load, or quiet and normal. The sensitivity of the microphone alone - forgetting the electronics in the phone - is typically ±4dB.
While the phone app will give you an indication, it will by no means be accurate. This is why I suggested measuring the same model so you’re not relying on any calibration.
If you can find a similar heat pump whose sound output is published, and measure that one with your app, you’ll have some sort of calibration for your phone.
Don’t expect accuracy or repeatable results - measuring environmental sound accurately is notoriously hard.
Nice work @QGgWW2WhH .
Given my experience of living in a town that sounds pretty believable.
One thing that I found interesting was that (of course) the sound intensity varies by frequency. Here’s my Ecodan 14kW at 1 metre:
ten_seconds_of_ecodan.zip (326.8 KB)
This was at 11:11 and it looks as though it was running at 3.2kW at that time - it’s max consumption appears to be about 5kW.
What I found with some similar devices that had a noise at a narrow frequency range was that by dampening the loudest frequency it made the perceived noise a lot less. In the case of my Ecodan it’s spread over quite a wide band so there’s not much point fixing that one frequency that is the highest in that chart. To be honest all I did to dampen the frequency of the other device was to put a towel over it.
Which leads me to the thing that I think really helps with my heat pump, which is the cushioned feet. It stops the low vibrations being transmitted to the solid floor and creating an annoying hum.