I have imaginery conversations with people who are real but not present and imaginery conversations with people who are imaginery. I only speak my side of the dialogue, the voices of the other conversationalists are in my head. These one sided conversations are out loud and often in public, though I try to avoid talking to myself where I will be overheard. Hands free headsets means loads of people apparently talk to themselves in public, much louder and far more randomly than my solitary efforts.

Talking to dogs and pets and wild animals doesn't count in my book because they are sentient and can hear, even if their response is non verbal.