I clicked on my book "LORNA" on my tablet the other day and nearly fell off my chair when somebody started to read my book. In other words it's also an Audio book somewhere and I could not find it again. I think it is an AB on Smashwords although I don't see it as an AB there. Strange.
Does your tablet have text-to-speech capability? Many digital devices do nowadays, and it may have been switched on by accident.