Have you ever known someone who lets you know audibly when they're not happy, even though they never say a word?

Sure, Sighs, eye rolling, pouting.

Sounds like classic ‘passive-aggressive’ behavior to me.
Are they doing this to each other, or toward the rest of the world?

They’re not actually “doing” it to anyone, they don’t even know each other, yet this is how they live their daily lives, regardless of who may be around.

I suppose I really don’t care much, except that one of them now lives with me and sometimes I just want to strangle her. For the most part, I just want her to be quiet and quit “harumphing” all over the house.

I can’t even begin to understand how one would address something like this.

Are they overweight? I could be misinterpreting what you’re saying, though I get the gist of it, but I usually think of these sounds as being associated with someone who has difficulty physically moving around. The first image to pop into my head of someone sighing or oofing while sitting in a chair or moving to pick something up is someone that is heavy.

@DigitalBlue No, neither of these women are overweight, they just seem to always be thinking they have the “weight of the world” on their respective shoulders.

I can’t figure it out – I think I’m mostly silent unless speaking. Maybe I do it as well? Maybe we all do? I don’t know.

Then it’s indulgent pseudo-nihilism. Woe is us, life is sooooooo tedious.
If it were genuine nihilism they would know it’s a waste of energy to complain that much.

Sure, loads of people do that… Or do I just know a lot of people who do that?
I’ve come across many people who do what you’re describing there @laurenkem.

A family member of mine does that. It’s tiresome at best, but it’s such an ingrained habit that I hesitate to complain. Fortunately I don’t have to live in the same place, so it’s not my problem.

I get the sort of silent treatment and disappointed looks. Which hurts more than being hit on the head with a frying pan (kind of!).

My S/O used to do that. I call her on it. Either speak up and tell me what’s on your mind or shutup. It drives me nuts.
@Shippy So good to see you stuck with us.

Everyone in my family does that, except the pre-schoolers who yell or even scream.

Never say a word? I would say the word never is extremely important in that sentence. I agree with @dabbler passive aggressive. If they just do it at times, but typically are good at expressing themseves and communicating, then stifling every so often isn’t necessarily a bad thing, but better if someone is not going to make a big deal to not make any noises or eye rolling in disgust, because really, who do they think they are kidding. They aren’t stifling at all, just expressigbtheir dissapproval in a different way.

Meanwhile, I would think all of us do some of those behaviors at times.

I’ve noticed that some old people actually growl if they feel you’ve inadvertently crossed them in some way.
It’s done in a covert, under their breath kind of way, but it’s definitely there, rather like a dog protecting it’s bone from a small child.