 Welcome back to World Hearing Facts. I'm Susanna Love. Have you ever heard that short ee-ringing sound in your ear? Perhaps while you were trying to fall asleep or you're sitting at a quiet lecture. That's the sound of damage to your hair cells in your inner ear. And most likely, you've just heard a hair cell signing off, telling you that it's now damaged beyond repair and you must rely on the remainder of your hair cells from now on. Here's what healthy hair cells look like. Perfectly organized rows of intact hair cells. And here, you see damaged hair cells, laying down, missing, swollen, no longer transmitting signals from the ear to the brain. We humans have been given around 15,000 hair cells per ear at birth and when they're gone, they're gone. So take good care of them. That's it for now. Join me again for more World Hearing Facts where you'll learn about how loud is too loud and what you can do about it.