April 27, 2017

Pardon? Like sensitive electronic equipment, ears can be easy hurt but also easily enhanced technologically

Damage to hair cells or to the nerve synapses they’re attached to is the most common source of hearing loss. Aging and noise are the leading causes; among the others are the chemotherapy drug cisplatin, the aminoglycoside family of antibiotics, and various autoimmune diseases, including the one that deafened (but didn’t silence) Rush Limbaugh. Corey showed me another electron micrograph, from the ear of a mouse that had been exposed for two hours to sound as intense as that experienced by someone using a chainsaw. The cilia looked like tree trunks thrown around by a tornado.

Hair cells can recover if a noise isn’t too loud and doesn’t last too long, but permanent injuries accumulate. A widely cited damage threshold for sustained exposure is eighty-five or ninety decibels. (The human hearing range is so wide that it has to be described logarithmically to keep the numbers from becoming unmanageable: every ten-decibel increase represents a tenfold increase in sound energy.) An unsettling number of everyday activities lie at or above the danger line, including lawn-mowing, motorcycle-riding, rock-concert-going, Shop-Vac-ing, milkshake-making, subway-riding, and power-tool-using. “Most carpenters have lost a lot of hearing by the time they’re fifty,” Corey said. “I’m sometimes around construction sites, and I often pass out ear protection.”