Learn English – word that describes the sound you make when you chuckle/breathe/cough in agreement with something

soundswriting

I am writing a novel and am constantly trying to figure out how to describe the action when someone gives a sort of small cough or a quick "huh" in agreement. I suppose it would be the non-word equivalent of "I'll say" or "You think?"
To be specific, I'll use it in a dialogue.

"He must really hate Ian, then."

Clarissa [insert word here]. "Yes."

It's usually used when the speaker is trying to convey that the subject is much more serious than their conversation partner is taking it.

Best Answer

Breath

It's called a sigh. Depending on the gravity of the context, an adverb may be used to add depth to the sigh, viz

"He must really hate Ian, then."

Clarissa sighed [resignedly]. "Yes."

Chuckle

In your use case, you're thinking of a snigger.

"He must really hate Ian, then."

Clarissa sniggered. "Yes."

Chuckle, as you already have it, should also suffice

Cough

The closest I can think of in this context is a grunt. I can't think of a situation where a cough is used as a sign of affirmation, unless the more recent sarcastic cough where a speaker makes a statement and someone (or the same speaker) coughs out a name as a snide affirmation, e.g.

Dorian: Some people just don't have boundaries

Oscar : ** cough ** Ian ** cough **

EDIT: A scoff might work here. It sounds like coughing somewhat, but it's usually applied in contempt, rather than resignation or despair (as I presume you're trying to portray)