It has been several years since I've been asked about this particular condition, known as somniloquy or sleep taking. I have done this myself in the past on occasion, after a particularly tiring, long day at a hectic occupation. There have also been times that I was either angry or laughing upon awakening from a dream, so I think all of these reactions are probably nothing to consider dangerous. However, your roommates may be disturbed by the noise. If it continues longer than a week, I advise you to seek professional guidance. it could be caused by some physical reaction or condition and this should be checked first.
Singing In the Dark
Several years ago, my circle of friends knew a young man that was almost addicted to professional baseball. He attended as many games as possible, watched them on television, collected baseball cards, memorized the statistics for the all of the members of his favorite teams, etc. I found that his true hobby was memorization. He memorized all the lyrics and dialogue of all the America musical productions of the 1960s - 1970s.
He memorized other material as well, including facts from American history and current - as many facts as he could find at the library and in classes. His idea of education was memorization, but so was much of the school system's.
You might be suspecting that he had some sort of mental disorder that is similar to that suffered by the Dustin Hoffman character in Rainman. I now wonder that myself. At the time, I began to suspect some neurological involvement, learning that alcoholism and substance addiction was evident in his family. He may even have inherited a learning disability from alcohol damage done to the egg and sperm that created him.
One humorous event in his life was a case of sleep taking. Actually, he was sleep singing. A parent found him standing upright at attention in bed one morning, singing the US National Anthem. If I recall correctly, he'd been dreaming of a baseball game.
All that aside, we can look at some information concerning sleep talking.
Sleep Walking, Sleep Talking
Possible Causes and Interpretations
Medicine tells us that sleep talking can be harmless and that most people do not remember the words they spoke while asleep. Some adults sleep talk for "no reason." Many more children up to age 10 do this, but I think it's the result of the fact that a child's brain and nervous system are not completely "done" (developed) until some few years later.
I think it must be related to sleep walking. However, doctors warn us that sleep talking can be attached to violence or a physical disorder. In these kinds of cases, an emotional shock such as the loss of a loved one or a breakup, or an extremely stressful event of some sort might be a precipitating event that overflows the glass of one's psyche and creates a sleep-talk event. Ask your own doctor for sure in your case.
The medical research suggests that most people, when they display sleep talking, do so only for half a minute, but some do this several times a night. It sometimes can become angry profanity or sexual material. Sometimes, it appears that the person is speaking to one or more other people, although witnesses see nothing. It might be a dream, although the sleeper will usually not recall it. In fact, the research shows in general that sleep talking can happen at any stage of sleep and not only during REM (Rapid Eye Movement) periods in which dreams occur.
In a spiritual analysis, some faiths and paranormal researchers might even interpret this as a visitation or spirit oppression. Watch the modern film The Fourth Kind for extreme cases of sleep talking.
Sleep talking can also be triggered by prescription medications, a mental health disorder, and substance or alcohol abuse, as well as emotional or other stress -- or a visitation in some schools of thought. Some people think that caffeine may also be a trigger for sleep talking. I'd agree, if caffeine was taken in a large amount or a person using it suddenly became sensitive or allergic to it.
Why Do People Talk In Their Sleep?
What to Do?
If you suspect a that sleep talking is a problem for you, keep a diary of what you ingest (food, beverages, medications, vitamins, everything), and when you sleep talk (a roommate can help with this). After a week passes and you feel you are sleep talking too much, take your diary on an appointment to your doctor or nurse practitioner and ask for help.
Another option is to volunteer as a subject at a sleep disorder clinic if related trials (studies) are being conducted in your town. You may even have referral to such a clinic from your doctor. Sleep talking can be related to sleep disorders that include sleep walking, Rapid Eye Movement Behavior Disorder, Night Terrors (these can be very serious), and Sleep-Related Eating Disorder.
Additional Health and Mental Health Links
Here are some links to other interesting presentations about life, health, and some odd occurrences that you might enjoy. Always contact your health provider if you suspect an illness that requires professional help.