Dear David,
I love visiting with my grandcat. But sometimes I have to talk loudly so she can hear me.
I asked my friend Christine Portfors why that is. She’s a biologist at Washington State University.
She told me it’s all about the hair cells inside our ears.
They aren’t really hairs. They’re sensory cells. Hair cells have tiny, bristle-like tufts that stick out—called cilia—that look a little bit like hairs.
Those hair cells are why we can hear.
First, sounds funnel into our ears. They bonk into the ear drum and make it vibrate. Then, three itty, bitty bones make those vibrations bigger. They send the vibrations to the inner ear. There are tons of hair cells there. The vibrations ripple over our hair cells, making the cilia move or bend. It’s like turning on a switch. Electrical signals zoom up the auditory nerve to our brains. Then, our brains make sense of what we’re hearing.
But, as we get older, our hair cells start to break down. After years and years of responding to sound vibrations, they simply wear out.
“The real problem is that hair cells can’t repair themselves or regrow,” Portfors said. “So, once they wear out, they’re gone—and you lose your ability to hear all those different types of sounds.”
Besides normal wear and tear, there are other ways our hair cells can take damage. Sometimes ear infections, head injuries and other diseases harm them. Sometimes medicines damage hair cells as a side effect.
Sounds that are too loud also hurt your hair cells. That’s extra true if the loud noises go on for a long time or happen regularly.
Maybe you’ve been somewhere super noisy or had your headphones cranked up mega loud. When things were quiet again, you may have heard a ringing sound inside your ears. Portfors says that’s your hair cells alerting you that loud sound is damaging them.
Luckily, it’s usually easy to protect your hair cells from loud noise. You can avoid very loud places—or only stay a short time. You can wear ear muffs or ear plugs when it’s loud. You can turn down your headphones. I learned that if someone else can hear my headphones while I’m using them, that means they’re definitely too loud.
Someday scientists will probably be able to fix damaged or worn-out hair cells.
“What’s interesting is birds and reptiles regrow their hair cells,” Portfors said. “So, there’s lots of research trying to understand why mammals don’t. Is there a way that we can understand the different genetics and help humans regrow their hair cells? That’s a huge area of study.”
In the meantime, use your ear protection—just like you use other safety gear like seatbelts and helmets. And if you’re lucky enough to have an older person in your life, help them stay connected.
It can be lonely to lose your hearing due to age, but spending time with you is ear-resistible.
Sincerely,
Dr. Universe