Sounds, noise of heating - ventilation?

Hello everyone,

for a few days now we have noticed (especially at night - since it is particularly quiet here) that for a certain period of time (about 5 minutes) a high noise level occurs in our bedroom (upper floor). We still do not know exactly what causes this - but we can only imagine that it is related to the heating.

It is a kind of "humming" (relatively loud, so you can really hear it) which disappears into thin air again after a few minutes.

Here are a few parameters of our house that might be important for your analysis:

- solid brick construction
- city villa with 2 full floors and cellar
- 2x concrete ceilings
- air-to-water heat pump completely installed inside the cellar
- central ventilation system in the cellar

Under our bed in the bedroom run 4 ventilation pipes - this is for your information, as we first thought that these noises must definitely come from the controlled living space ventilation, however, this noise disappears, which makes me quite sure that it cannot be the controlled living space ventilation?

What we have also observed:

According to SolarEdge (photovoltaic system app) we can see that these noises occur shortly after the "warm-up peaks" of the heat pump. So I almost suspect that the noises form when the underfloor heating heats up properly.

However, in the upper floor (in the two children’s rooms and the bathroom) this noise cannot be heard in any other room - only in our bedroom.

Maybe someone has an idea what it could be? Unfortunately, my heating engineer is currently on vacation and I would like to gather opinions or ideas about what it could be before I talk to him.

I am grateful for any tips!

Sounds to me like defrosting processes of the heat pump. The pump really speeds up for a few minutes...

sounds like defrosting processes of the heat pump to me. The pump speeds up really high for a few minutes...

Totally strange... this morning we heard it extremely loud in another room. The noise was gone after about 5 minutes (you could really hear how it slowly got quieter and then disappeared)...

I just don’t understand how you can hear that in one room and not in the other?

I don't think it's the underfloor heating itself, but the device installed indoors. Is it properly decoupled from the wall?

I don't think the problem lies with the underfloor heating itself, but with the device installed indoors. Is it properly decoupled from the wall?

The device is decoupled on a concrete base in the basement using edge insulation strips. I also laid the tiles correctly and always paid attention to the decoupling at the tile baseboards.

If it were not properly decoupled, then it would have to make noise either always in the same room or more permanently, right?

We also have an air-to-water heat pump installed indoors. Also decoupled on a concrete base, etc. Whether this was executed 100% I cannot say. For us, it is like this: when the heat pump runs at full capacity, which was at the beginning with hot water and defrost cycles, we also heard a humming sound. Also in the phase before last winter when it was -20 degrees. I cannot prove it but I am quite sure that it is structure-borne noise being transmitted. Because it can only be heard in two rooms. What I did was check the hoses/pipes going off again. One actually had contact with the wall. I also then limited the maximum hot water output (and scheduled it during the day) and I think also during the defrost cycles but to be honest I don’t remember anymore. After that, it was definitely better. Our heat pump is an IDM ILM 2-7.