Sleeptalking

Also known as "somniloquy." Sleeptalkers utter speech or sounds while asleep, without any awareness of doing so.  Sleeptalking can occur in NREM and REM sleep.  It is extremely common in children, less common in adults.  Sleeptalking is often associated with sleep deprivation, and so may have some of the same root causes as sleepwalking. 

Dement, The Promise of Sleep