If you've ever fallen asleep to the gentle sounds of white noise played through a set of wireless earbuds, you'll know just how soothing it is to let the din of a rainy forest or ocean waves beckon ...

Here’s how it works. First, place the tip of your tongue against your two upper front teeth, and keep it there. (The goal is to inhale and exhale around your tongue.) Then: While inhaling and exhaling ...