5 Thou shalt not mutter, whisper, blurt, bellow, or scream, for it is the words and not the characterization of the words that must carry their own decibels.
Continuing with Sol Stein's Ten Commanments for Writers, I cringe, and whisper, "I have trouble with this one." Not so much the other characterizations, but the whispering-- that's going to haunt me until I get my ms back from my editor with the question marked in large, red scrolling letters,
"What's with all the whispering?"(I really don't know what my editor's handwriting looks like yet, or even if it comes back to me hand or electronically marked... learning, learning, learning...)
I've read a dozen articles or tips about sticking to "he said" or "she said", or using no dialog tags at all (which I prefer if I can get away with it). So why is it so difficult to trust our readers to know that the character is whispering? Or SHOUTING, or blurting?