The sense of hearing is a mixed blessing. Think of the joy of listening to your favorite music. Or the comfort of a heart-to-heart talk with a parent or good friend. Now recall the sound of an ambulance screaming along the road. Or the terror of an unexpected sound when you are almost asleep at night. Joy, comfort, agony, and terror—you experience them all because you have ears.
Your ears can hear all kinds of sounds. You can hear the bone-shaking noise of a jackhammer. You can also hear wind rustling the leaves of a tree. But there are sounds you can’t hear. A dog whistle is too high for your ears to notice. And you never hear most of the sounds your body makes: joints creaking, stomach churning, eyelids fluttering. Your body ignores its own sounds so you can focus on whatever your brain is really interested in.
