Why do adult people make grunting and moanin noises in their sleep?

Depends.: It depends on the type of noise. It could be normal dreams, sinus problem or people with obstructive sleep apnea will make noises, gasping for air as they have a very difficult time breathing or inhaling enough throughout the night. This is a serious medical condition that should be determined and addressed appropriately as this places extreme stress on the body. See a physician for evaluation.