Rolling ocean waves and the low rumble of a distant thunder storm are known to put a person to sleep, but have you ever wondered why these sounds are so calming?
In part, it is because the brain interprets these sounds as 'non-threats,' according to an associate professor from Pennsylvania State University, and it can use them to block out other, more alarming noises.
While a shrill sound can jolt you out of a deep sleep, the pattering of raindrops in a quiet forest will exist peacefully in the background.