At Bread Kitchen, couldn't help noticing woman gesticulating to another. Giving gang signals? Describing dance moves with hands? Daydreaming with finger tic? Lunacy?
None of these, but SIGN LANGUAGE, it finally dawned on observer who couldn't help noticing. Theirs was animated, soundless conversation.
There is also lip-reading. The most famous lip-reader I know is Henry Kisor, recently retired Sun-Times book editor. He had an editor once who barely moved his when speaking. Didn't stop Henry. Nothing did. He also wrote a book about being deaf.