I have worked for many years with the hearing impaired and on a visit to the library, I happened to notice a man and a woman, both deaf, signing with intense gestures, apparently in a heated debate.
The man said something, and the woman seemed upset. She started signing her reply very fast, to the point where the man couldn't understand a word. That was when she started signing in big, wide gestures.
Finally, looking strained, her companion took her hands, "silencing" her.
Then he signed, very small and slowly, "You don't have to shout, I'm not blind."