Snoring happens when the flow of air through the mouth and nose is partially obstructed during sleep. This causes the surrounding tissues to vibrate, producing that familiar, often loud noise. "Snoring is a sign that there is a really narrowed space," says Dr. Sanjay Patel, a sleep disorder specialist at Harvard-affiliated Beth Israel Deaconess Medical Center. "That happens either in your nasal passages or in the back of your throat." [2] Snoring can be caused by a variety of factors including the anatomy of your mouth and sinuses, alcohol consumption, allergies, a cold, or your sleeping position.