If you, like me, have used a white-noise machine to help your wee one sleep, you probably had a panic attack when you saw the headlines Monday morning. “Warning: Infant sound machines may lead to hearing loss,” screamed CBSNews.com. “Popular Infant Sound Machines May Be Hazardous to Babies’ Hearing,” warned the Huffington Post. Similar scare stories appeared on the websites of Fox News and USA Today. My favorite was Health Newsline’s headline, which claimed that sleep machines can cause deafness.
These stories were all based on the results of a single study published in Pediatrics. And although the study raised questions about how white-noise machines should be used, it didn’t show that the machines caused hearing loss or deafness. In fact, “not a single infant was harmed in the study,” explains lead author Blake Papsin, a pediatric otolaryngologist at Toronto’s Hospital for Sick Children—because no babies were involved in the study. Moreover, many of the articles covering the study emphasized that every single one of the sound machines exceeded a “recommended noise limit,” yet this limit has nothing to do with infant safety or hearing loss at all.
First, let me briefly describe the study. Papsin and his colleagues at the University of Toronto and the Hospital for Sick Children tested the loudness of 65 white-noise sounds emitted by 14 infant sleep machines when these machines were set to maximum volume. They recorded how loud the machines would be when placed a little under a foot from an infant’s ears—if, say, you put a sleep machine inside your child’s crib or mounted it on the crib rail—as well as how loud the machines would be when they were placed 3 1/4 feet or 6 1/2 feet from infants’ ears—so, on the nightstand. They made mathematical corrections to account for the fact that an infant’s ear canal responds to sounds differently than an adult’s does. Overall, they found that, at maximum volume, every one of the noise machines placed within 3 1/4 feet of infants’ ears were capable of producing sounds that exposed the babies to more than 50 A-weighted decibels, what the study describes as “the current recommended noise limit for infants in hospital nurseries.”
That sounds bad, right? Well, I was curious about this “recommended noise limit,” so I did some digging—and it turns out that the limit, recommended in 1999 by the National Resource Center, has nothing to do with protecting infants’ hearing. It was set for neonatal intensive care units, or NICUs, with the primary objective being “to preserve a large portion of each hour for infant sleep.” Sleep is crucial for premature infants, and loud noises startle and bother NICU babies more than they disturb full-term healthy babies, so the limit primarily exists to help premature babies snooze better. That’s funny, because helping babies sleep better is, of course, exactly why parents use white noise machines. The 1999 report even addressed whether loud NICUs might hurt premature infants’ ears and concluded that, “not surprisingly,” harmful effects from loud NICU noise “have not been demonstrated consistently.”
And white-noise machines do seem to help babies sleep better. The idea behind white noise is that it masks sudden sounds (doorbell, dog barking, older brother screaming), making it easier for babies—and, well, everyone—to fall and stay asleep. One small trial found, for instance, that more than three-quarters of newborns fell asleep within five minutes when they were exposed to white noise, compared with only a quarter of newborns who tried to fall asleep without it.