Nighttime noise can refer to a variety of sounds, such as snoring and the sound of someone sleeping, which is often represented by 'ZZZ'. Snoring is a common sound heard during nighttime, and is caused by the vibration of the soft palate and other tissues in the throat. It is usually caused by a blockage of the airway, which can be caused by a variety of factors, such as allergies, colds, or even obesity. ZZZ is a sound that is often used to represent the sound of someone sleeping, and is usually accompanied by a picture of a person snoozing.