Dear yin-yang,
Most people snore to some degree. Generally speaking it is quite normal. If snoring gets to the point where it becomes extremely loud and bothersome to others, then this degree of snoring is not considered normal. Snoring is much more prominent in men than in women.
Snoring is most often caused by loose, weak, or excessive tissue at the back of the throat which collapses into the airway during sleep. This tissue flutters or vibrates as air is breathed in. This fluttering tissue, like a flag flapping in a strong breeze, is the cause of the aggravating noise we know as snoring.
During sleep the muscle tissue that causes snoring tends to relax. The deeper we fall asleep the more relaxed this tissue becomes. This relaxed tissue will begin to cover the airway and thus the snoring sound begins. This is why we usually do not hear ourselves snore. By the time we start to snore, we are in a deep enough sleep not to hear the noise.
Treatment of snoring includes C-PAP, Dental appliance to Surgery. Ask your friend to consult an ENT specialist for furher evaluation and its definite treatment.
Following link would be useful to you:
Hope this information helped you.