Unvented System Expansion vessel Running Loud?

[Silveretta]

Hi all, first time visitor to these forums, hoping you can help!

As a quick background, I've just moved house, and am now renting a room with a couple who have just gone away for a holiday - typical! The house is relatively new, having been built probably around 5 years ago.

There's a constant noise which sounds similar to an extraction fan, and keeps me up at night. I've narrowed it down to what I believe is called an unvented system expansion vessel, although I'm a little confused.

I've put a few images up here https://imgur.com/a/DF3Tp4j, but am not sure what people would want to see.

My main question is to whether this noise is normal, and if not, what I can do to stop this, please!