The temperature in your bedroom is perfect. Your blackout curtains have been drawn shut. And you’ve just finished a cup of chamomile tea and novel that made you laugh out loud and forget about whatever was bothering you earlier in the day.

You’re just about ready to drift off, and suddenly the air conditioner kicks on. Or a car alarm screeches through the night air. Or your partner sneezes. Suddenly, you’re wide-awake again. Your brain responds to noises when you’re awake and asleep. But if the interruptions wake you up, that can keep you from getting the restful shuteye that you need.

When ambient noise is disrupting your sleep, white (or pink) noise can help to smooth out the rough edges. Imagine sitting next to a person who is loudly chewing gum in a library. Then imagine sitting next to that same person in a crowded bar. It’s the same chomping gum, but underneath the drone of a crowded place, you can’t even hear it anymore. White noise, whether it’s from a sound machine, a simple fan, or crowd noise helps to mask noise-related disruptions by creating a constant ambient sound that makes a “peak” noise, like a door slamming, less of a contrast. And that makes you less likely to be startled awake.