The sounds of rushing water have been soothing Jessica Strong’s daughter, Gwenyth, to sleep since she was one month old. She would only drift off when her parents rocked her in the bathroom with the water running in the tub. Then, she moved on to a motorized swing with a built-in “rushing river” sound effect. These days, Gwenyth, now two, falls asleep in her crib to a soundtrack of water noises playing from an iPod plugged into a speaker.
Strong, a mother of two from Windsor, Ont., is one of the many parents who rely on white noise to help their babies sleep, or drown out any sounds that might wake a light sleeper. Noise machines disguised as cuddly stuffed animals are popular on baby shower registries, but a household fan or smartphone app can work, too—in fact, it’s a practice recommended by several popular parenting books and sleep doulas. But a recent study from researchers at The Hospital for Sick Children in Toronto found that some infant sleep machines produce sounds that could increase risk of noise-induced hearing loss.
The study tested 14 infant sleep machines currently available in stores (but never released the brand names). To approximate the audio levels when the devices are placed in your baby’s crib, near the crib and across the room, they measured sound levels at about a foot away, a little more than three feet away, and six-and-a-half feet away.
Three of the machines they tested exceeded 85 decibels when on the highest volume setting, at the “in the crib” distance. That’s about as loud as a hair dryer or blender, and spending eight hours or more at 85 decibels or higher has been shown to cause hearing loss in adults. (It also exceeds occupational health guidelines for the workplace.)
Blake Papsin, paediatric otolaryngologist-in-chief at SickKids and one of the authors of the study, says that if 85 decibels is too loud for adults, then it’s probably too loud for babies. But because there haven’t been any studies of infant hearing loss due to sound machines, it’s impossible for him to say how much sound is safe. “We know 85 decibels is harmful for adults, so is 60 decibels going to be safe? Maybe, but not if it’s on constantly, all night.”
Until researchers know more about the impact of sound machines on infant auditory development, Papsin thinks parents should err on the side of caution and follow the same guidelines in place for neonatal intensive care units, where sound is supposed to be 50 decibels. However, 50 decibels is fairly quiet—about the equivalent of a normal conversation or office environment—and all 14 of the sound machines Papsin tested exceeded 50 decibels when placed in or near the crib. Following the 50-decibels-or-less guideline might mean cutting out the machines altogether.
After Strong read about Papsin’s study, she says she felt like a terrible parent but decided to do her own research. She downloaded a decibel-measuring app on her smartphone and checked the levels in the nursery. At her daughter’s pillow, the sound measured in the 55 to 60 decibel range. “Sixty decibels is equivalent to a conversation, so I feel comfortable with that,” she says. They still use the iPod nightly, but Strong turns the volume down after her daughter falls asleep.
Papsin advises placing sound machines as far away from the crib as possible, on the lowest setting. Turn them down, or off, once a child has dozed off for the night. “I’m not saying you’re a bad parent if you use these machines,” says Papsin. “But they aren’t regulated at all, so just think about lowering the dose,” he explains.
Strong still wouldn’t hesitate to recommend white noise for baby sleep to parents struggling with a colicky or sleep-deprived baby. “If your child isn’t sleeping and it’s affecting your mental health, I think a bit of noise at a reasonable volume is worth the trade-off,” she says.
A version of this story appeared in the July 2014 print issue with the headline, "Sound asleep," on p. 52.