[theme music] We usually describe it as a ringing, but it could come to you as a hiss, a crackle, or a buzz and happens to that 20% of us, unless you’re a rock star in which case MAYBE I SHOULD TALK LOUDER! Ringing in the ears called tinnitus or tinnitus [differing pronunciation], whichever tomatoes your tomato [differing pronunciation], can be caused by a number of things from neurological disorders, to ear infections, to allergies, and even stress. But the most common cause is exposure to loud noises. Even though the ringing seems like an annoying sound, tinnitus is actually a sign of a loss of hearing, which could be temporary or forever. To understand tinnitus, we need to talk about how sound reaches your brain, because sound is a physical wave, but your brain only speaks in electrical signals. So for you to be able to hear sounds, you have to convert those sound waves into electrical information that can be fired down your auditory nerve and into your brain. Thankfully, we have all kinds of hardware in our ear to help us do that. It’s a more complicated process then we’re going to talk about today, but the important thing is that sound waves make your ear drum vibrate and those vibrations are amplified and sent along your cochlea. You can imagine your cochlea as a tuning fork with a membrane stretched between the two tines. That membrane is covered in special cells called hair cells because they’re shaped like tiny hairs… …but they’re not hairs. Some are short and bristly and some are long and flowy, and when the tuning fork vibrates the frequency determines which of your hair cells will vibrate with it. High frequency sounds make the short thick hairs move, while low frequency sounds move the long flexible hairs. Quiet sounds move the hairs only a little, but loud sounds make them thrash around like headbangers, and really loud sounds, like 90 decibels or higher, louder than a lawn mower, they make your hair cells whip around so hard that the tips actually break off. And since those cells are what tell your brain when noise is happening, if they get damaged, your brain can get confused about whether it’s supposed to be hearing something or not. Because when hair cells get broken, they don’t just turn off. . . …instead they start to leak little trickles of electrical impulses. Your brain, in turn, interprets these leaking impulses to be a sound that sounds like [HIGH PITCHED WAVERING SOUND]. Essentially, your brain’s auditory center just starts to assume that there’s noise when there’s no noise. Usually, the tips of your hair cells grow back in a couple of days but, if they keep getting damaged, those cells can die. And you don’t get new ones. Which means that for some people tinnitus can become a lifelong condition. So rock on, people… …but rock safely… …and thanks for asking! Thanks especially to our Subbable subscribers who make it possible for us to keep answering the internet’s most ‘FA’ed Qs. To find out how you can help support us, just go to Subbable.come/scishow, and if you have a quick question, let us know on Facebook, or Twitter, or in the comments below and don’t forget to go to YouTube.com/scishow and subscribe. [theme music]