Let your pylons discharge to 50%. Then charge them back up, you will hear the fans after charging for a while.
Maybe go ask about the noise on Community if you think it’s abnormal, if others with the 10k Multi experience the same then Victron will probably look in to it. I know in the past noise issues was addressed in firmware updates.
There was a discussion quite a while ago on Community in which I posted, where a guy wanted to rip out the noisy fan of his Multi, a good quality fan plus rubber mountings makes a huge difference, but this is obviously not a option for you at this stage.
Is it just the fan or actually the transformers making some of the noise? There is a reason why they call low frequency welders buzz boxes…
My MLT makes the same humming sound when charging from the grid. It’s normal for transformer base inverters to do that. You must come listen when you adjust it 100%, then it sounds like a sub station in my garage. 
and the next door guy lights starts flickering.
I don’t really think the noise is abnormal: there’s no scratching or anything like that. The pool pump also doesn’t make it “grunt” like you can get from starting an inductive load.
Here’s the thing’s guts:
The transformer is definitely the culprit for the hum, and yes, all transformers do that. However, since all transformers do that, it shouldn’t be a surprise to the engineers designing an inverter and at least some noise mitigation is expected.
In this case (literally) no attention seems to have been given to reducing vibration, dampening it, whatever else one can do. I can’t speak to the quality of the fans, but they’re hard-mounted with no grommets.
It’s silly to produce a device with an IP21 rating that then makes too much noise to be used in a house.
Since I actually trust the warranty (erm, this photo is of a different one… at a friend’s house), I won’t be messing with it in terms of replacement fans or so-on. So it will have to move.
(In case you think I’m just whinging and I could have known it makes noise: I did know: I had a MultiPlus 3kva for 5 years, so I expected some noise here. I did not expect a new design 8kW sustained inverter to sound worse at 2kW than that one at full load.)
aaawwwwwww that is cute little Toroidal. You still need to go check a MLT one then. @TheTerribleTriplet will tell you how big they are after I open one of the two inverters for him. Noise is caused by magnetostriction (changes in shape) of the core laminations while the transformer is energized. So the bigger the transformer or Toroidal, the noisier they are. @Stanley will tell you the same thing with the bigger MLT inverters and @plonkster.
This is the inside of the one inverter of mine.
The Toroidal is massive in this inverters.
My two multis are in the garage and i can hear them when I’m running full steam but it doesn’t bother us because its other side the kitchen wall.
I’m pretty sure it wont be the last item you will end up moving or changing
wow you really take that seriously, even polishing the inside of your inverter
Yoh, that’s quite a microwave you have there.
It’s a sign that they are working. 
I can hear mine slightly but you you need to stand close to the garage door inside the house. when you inside the garage, then you can hear them making the music.
hahhahahahahh!!! clean inverter, happy inverter 
hahaaha, the can was there for comparison of size, but is was busy cleaning the inverter outside.
In those very old powerstars that is a big inductor which goes between the AC input and the inverter output. The reason for it was that it allows you to have a different voltage on either side of the inductor, which meant that you can do voltage regulation and also clean up the AC which was very nice if you used a generator as your AC source. IIRC you could regulate the output by up to 20V, so the load would see 230V when the input was anywhere from 210V to 250V. Those were removed at some stage because of NRS, since doing voltage regulation like that decreases the power factor of the power pulled from the AC input. Anyway, that big inductor has an air gap and is quite close to the side cover, so the magnetic field causes that side to vibrate slightly and the magnitude of the vibration will depend on the current drawn from the AC input (since that is what goes through the inductor) hence the volume being dependent on the charging current.
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Jip, al 80kg in it’s glory, and that is still the small one. Got the 8.0H and the 10.0H.
So I’m paraphrasing from the Community forums:
Victron is powered by Multiplus II’s and this is why they cannot hear us complain
Edit: Our very own @Bobby is the progenitor of the thread, keeping an eye on this one.
Correct. @mariusm which firmware version are you on? There was a bug fixed in 489 (Oct 2021) that reduced the humming noise. Pretty sure you’ll already be there seeing how it’s a new unit, but just thought to mention it in case.
That’s why it was on 75% when you called yesterday. Just been happily playing around with ESS values to let it discharge a bit, hear the noise and let it charge. When I went to charge yesterday it went into slow charge though, but I just left it.
I’ll do a “can we make the night” test soon in any case, but with this weather in Jhb today I’m worried that mist might cause some power stations to trip…
Production usually settles on a specific version for longer periods, which means you should not count on your inverter arriving with recent firmware, by which I mean 6-month old firmware is not out of the norm. You also don’t know how long that inverter was in a warehouse, and the supply/demand/flow for different models might not be the same. Installers are taught to update the firmware to the latest during installation.
Marius, being the pro he is, would have done that already, right?
You mean it used to be worse?!
Yeah, I installed the latest firmware immediately (497). Didn’t check what it shipped with, assumed it’ll be some arb version. (You want constant firmware during production so that QC doesn’t have to deal with issues that may be caused by firmware. Some manufacturers then plonk down a newer one as they go out the door, but even that wouldn’t be the latest, just in case it causes problems again.)
What makes me saddest is that there’s NOTHING in there to dampen, so they didn’t even try. @plonkster you should feel bad. 
Always DEV’s fault…
Yes and no. The release notes specifies this:
Fix small PLL issue introduced in xxxx483 which in some cases can cause audible noise.
So it got worse with 1 version, picked up and fixed in a later version.
Just in case someone takes this the wrong way… I assume @plonkster takes professional pride in his work, as well as that of the wider company, even though he has nothing specifically to do with it.
I am the same, and I feel a pinch of guilt when I see my company has failed a customer in some way, even though I had nothing to do with it, and no specific way to affect the outcome.
But I do raise it internally. If you see something, say something.
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This forum has some tough audience members
I wouldn’t dream of installing an inverter in my living area unless it was 100% necessary… for many reasons but noise is 1. “Inverter = batteries close by” is high on that list.