Wave sound repeats in a steady rhythm, it rises, breaks, pulls back. That cycle sits remarkably close to the natural rhythm of human breathing, which is why the body unconsciously starts matching its breath to it.
As breathing slows, heart rate slows with it, which nudges the nervous system into a calmer state. So wave sound isn't just pleasant, it's a mechanism that actually slows the body down.
That's why, at the end of a heavy day, ocean sound often brings relief faster than other nature sounds do.