The central symptom of sleep talking is audible expression that occurs during sleep without the person being aware of it happening.
It can be gibberish or resemble normal speech and consists in the unaware production of vocalisation during sleep.
However, people are very rarely aware that they are talking in their sleep at the time and typically have no recollection of the episodes when they wake up.
A large number of sleep speeches merely consist of short expressions of assent or negation (e.g., ‘OK’, ‘no,’ ‘good,’ ‘mm-hm,’ ‘uh-huh,’ ‘no!’ ‘stop!’ ‘don’t!’, etc.)
As they experience different sensations and emotions in their dreams, it may manifest as groaning or other vocalisations.
Excess mucus, combined with nose breathing and narrow airways, can lead to rattling or whistling sounds. Congestion and dry or swollen nasal membranes can clog up the works
making breathing audible instead of peaceful. Sometimes it’s occasional, a gentle, perhaps even peaceful, soft whistling.
Other times it sounds like a buzz saw, getting closer and closer, paused by a moment of silence, before climaxing in an even louder snort or gasp for air.
And sometimes when we fall into a deep sleep, the muscles in the roof of the mouth (soft palate), tongue and throat relax. The tissues in the back of the throat can relax enough
that they partially block the airway. As we inhale and exhale, these tissues rattle and vibrate, resulting in sounds in some people. The tissue vibration increases as the airway
narrows, causing the snoring to grow louder and louder. As a person inhales and exhales, the moving air causes the tissue to flutter and make noise.
Usually during sleep the brain becomes used to one’s own snoring (a process called habituation)
As mentioned, people sometimes don’t hear themselves snore because the brain’s ability to receive sensory information is limited while we sleep.
Some external stimulus may cause a person to stir, however.