It seems like such a good idea. As so many get-the-kid-to-sleep tricks do. But new research shows that using a machine that produces soothing sounds to lull a baby to sleep might damage his or her hearing.
A study published in Pediatrics last month analyzed 14 popular sleep machines at maximum volume and found that they produced between 68.8 to 92.9 decibels from 30 centimeters away. That’s about how far one might be placed from an infant’s head. Three of the machines exceeded 85 decibels, which is what the National Institute for Occupational Safety and Health deems the threshold of workplace safety for adults over the course of an eight-hour shift.
One of the baby machines was so loud that two hours of use would exceed workplace noise limits.
At 100 centimeters away, all the machines tested still were louder than the 50-decibel limit set in 1999 by an expert panel for an hour’s exposure in hospital nurseries in 1999.
“These machines are capable of delivering noise that we think is unsafe for full-grown adults in mines,” Dr. Blake Papsin told the New York Times. He is senior author of the study, and the chief otolaryngologist (disorders of the ear, nose and throat) at the Hospital for Sick Children in Toronto.
“Unless parents are adequately warned of the danger, or the design of the machines by manufacturers is changed to be safer, then the potential for harm exists, and parents need to know about it,” Dr. Gordon B. Hughes, the program director of clinical trials for the National Institute on Deafness and Other Communication Disorders, told The Times.
Newborn brains are learning to differentiate sounds at different pitches even during sleep, according to Lisa L. Hunter, scientific director of research in the division of audiology at Cincinnati Children’s Hospital. “If you’ve conditioned them to white noise, there’s every indication that they might not be as responsive as they otherwise should be to soft speech,” she told The Times.
The idea behind infant sleep machines is that their white noise or nature sounds drown out the normal ambient sounds that can disturb a baby’s sleep — voices, vehicle noise, music, etc. The machines come in many forms, including embedded in stuffed animals, and frequently are recommended by parenting books and websites.
Even some sleep experts advise parents to use them all night, every night, and many parents say their babies become so used to the sounds of rainfall or birds that they will not nap without them.
Despite their apparent potential to damage hearing, sleep machines can be used safely, according to the researchers. Papsin suggested placing the devices farther away, lowering the volume and using them for shorter periods to deliver less sound pressure to the baby. That means you should be wary of the models designed to be affixed to the crib.
The researchers also recommended that device manufacturers limit the maximum noise level of infant sleep machines.
Dr. Marc Weissbluth, a pediatrician and author of “Healthy Sleep Habits, Happy Child,” agreed that you don’t necessarily have to throw out the baby noise machine with the bath water. He told The Times that parents could use one, if they were careful. “If it’s too close or it’s too loud, this might not be healthy for your baby,” he said. But “a quiet machine that’s far away may cause no harm whatsoever.”
Maybe. But one Times reader posted an interesting comment to the story: “If the sound of a sleep machine is dangerously loud, I hate to think about all of the noise my premie was exposed to while in the n.i.c.u. [neonatal intensive care unit] for several weeks. Constant beeping, lights on, etc. I don't think she's worse for the wear, but hospitals need to be much more mindful about all of the environmental noise babies are exposed to in the n.i.c.u.”
To learn more about babies and sleep, see our blog, “Getting Your Baby to Sleep.”