Tween Science
Winter 2014

Kids and dogs have a lot in common: they’re cute, like to play, and have better hearing than adult humans. Teens and younger kids can hear frequencies up to about 20 kHz. But by the time we are 30 or so, most humans can’t hear frequencies much above 14 kHz. In fact, some crafty kids have found a way to stealth-text by using high-frequency ring tones that adults can’t hear! Why the difference? We actually start to lose our ability to hear higher frequencies during adolescence. Inside our ears are tiny sound sensors called hair cells (so named because they are long and thin, like hairs). Sound waves cause air pressure to change inside our ears, bending the hair cells, which transmit the sensation to the brain. If the sound is too loud, the drastic change in air pressure can bend the hair cells too far and kill them. Different hair cells are sensitive to different frequencies. Once hair cells die, you lose the ability to hear that frequency forever— mammal hair cells cannot regenerate. For some reason, hair cells that detect higher frequencies seem to die young. It’s not clear why this is, but perhaps they are more fragile than hair cells that detect lower frequencies. Hearing loss may be inevitable, but to prolong your high-frequency advantage over the geezers, consider keeping the volume below a dull roar.