What is the term that describes writing uot a sound... For example, if I type "hm HHMMmmm hmmhmm hmm" when someone hums a tune or something like "My car made a funny noice, it sounded like rrr...rrrrrr....rrrrrrr.RRRKKKKKkkKKKKsc
EDIT: It's onomatopoeia. Which used to be one of my favorite words! I can't believe I forgot!