I was fine chattering away to myself, singing or making sound patterns, in order to close out the impact of the invasiveness of others, and being told to shut up only heightened the desire to surround myself with the sound of my own voice. If I was expected to reply, however, this was the complete antithesis. Hearing myself speak in my own voice in acknowledged connection to the world was excruciatingly personal and felt like fingernails down a blackboard.

Source: Williams, Donna (2002-09-14T23:58:59). Exposure Anxiety – The Invisible Cage . Jessica Kingsley Publishers. Kindle Edition. 

I’m also a vocal stimmer who shuts down when speaking.