My husband is fond of sighing, huffing and muttered exclamations and it drives me mad. Lots of "Oh God/FFS/Really?!!" as well as loud sighing/huffing - all without any precursor or context. Often it's related to him reading work emails and messages. But also it can be about things he sees around the house like mess left by the kids. I agree that does absolutely annoy me too, but I think I tend to be more direct about it.
Why does he do this? At my most uncharitable I think it's attention seeking or trying to seem important/highlight how stressed he is - or just downright passive aggressive.
If you live with a huffer and puffer how do you deal with it? If you are one, do I need to be kinder?