Weird noises only heard by my wife

My wife (36f) and I (36m) bought and moved into our 30 year-old house around 3 years ago. She just told me some things which sent chills down my spine. She told me about strange noises and experiences she has heard/had since we moved in. At first it was insignificant and few and far between, so she had brushed it off and said nothing. But lately it's been more and more frequent and significant, which is why she decided to tell me.

She told me that at first, it would be noises in the attic. Like thumping noises or footsteps. She would go check and see nothing there. But recently it's been at different places in the house. She mentioned that she's heard short thumps on our stairs multiple times, as if someone would take 2 or 3 hard steps just to let everyone know they're there. At other times she'd hear a very clear and loud sigh, when sitting on the couch for example. This would sound like it's no more that 1 or 2 metres away. Again, as if someone wanted to let their presence be known. And again, the attic noises.

Now, one significant piece of information she told me was that she only hears these noises when I'm either sleeping or not in the house. She never hears them when I'm at home and awake. This was a pattern she's very clearly noticed, and I have indeed never experienced any of the things she talked about in this house. I obviously do believe her; my wife's not someone who would make up such things, or think any little "house-noise" is anything significant. It has also very clearly affected her; as she was telling me this she started shaking and crying. My question is what this can be or mean? Is there some entity causing this and why does it only make its presence known when I'm not around or asleep? And what could it want?

As a side note, I myself haven't experienced the things my wife has, but I do have my own weird experience. I get the same terrifying and intense nightmare from time to time: that of an extremely dark entity or energy chasing me or my loved ones. It happens once every few months and it's always the same kind of dream; the entity is very dark and is after me, and as I repeatedly try to recite religious texts to chase it away it won't allow me. So I keep running, and at one point it closes in on me and I wake up afraid and breathing heavily. It may just be a dream and mean nothing at all, or otherwise have nothing to do with the story above, but I thought it was worth mentioning.

Edit: thank you everyone for your comments and suggestions, I'm sorry I haven't been able to reply yet but I promise to reply all of you asap. Will also add a small update soon.

Update: so last night I had a work thing and was away all through the evening and most of the night. My wife was watching TV, sitting on a couch in front of a wall. On the other side of that wall is the hallway which leads to the front door and stairs. She told me that at one point she heard the strangest sound through the wall coming from the hallway; she described it as a rhythmic moaning/grunting sound. This went on for minutes. She decided not to go look, partially out of fear and partially because she thought that if she didn't give it any attention it would go away, and that giving it attention would only strengthen it. We both don't know if it was the right course of action but sure enough it did stop. Nothing else happened after that. I did ask her why she didn't record it, and she didn't quite know why she didn't think of it at the time. She will next time though.