Term for the type of audible reaction typically written as "heh" or "hmph"

Is there a term for a person's audible reaction, the quoted written form of which we typically find spelled as heh or hmph?

I think they express different sentiments (and thus call for different words).

Heh (a slight laugh) could be described as a chuckle.

Hmph (a sound of disapproval) could be described as a harrumph.

I think the word you're looking for is "onomatopoeia".

A female friend who was baffled about why her husband wasn't having some minor health problem seen to said

I told him he needed to go see the doctor.

I suggested that he had

responded with an inarticulate grunt

She agreed and was--perhaps--enlightened. At least she bullied him into giving a real response and eventually into seeing the doctor.

Anyway, it's not a single word or a particularly sonorous phrase, but I think it covers the whole category. Learning to interpret the ones your SO uses is a whole different problem.