Answer: A: An author is allowed quite a bit of slack when writing dialogue in a story. So one writer may spell Jason’s scream as “ah,” another as “ahh,” and still another as “a-h-h.” The same may be said about Michelle’s moan and Nancy’s swoon and Henry’s wondering.
Try to be consistent, though. If you use “a-h-h” in one place, stick with that spelling elsewhere in the story.
if in doubt, you can always look it up. You’d be surprised at how many of these words are actually in the dictionary. For instance, The American Heritage Dictionary of the English Language (4th ed.) has three of the words you mentioned, with these spellings: “ah,” “oh,” “aw.”
I sometimes use hyphens when I stretch out one of these words: “a-h-h,” “o-o-h,” “a-w-w,” and so on. But another writer may skip the hyphens. It’s a judgment call.