Many parents of newborns swear by white noise machines as the only thing that can get their infant to sleep for prolonged periods of time. But a new study now suggests that some ambient sound machines specifically marketed for infants may actually damage their hearing.
Infant sleep machines are designed to produce white noise that override other sounds and help a baby drift to sleep. There are hundreds of sound machines on the market, and some of them have even been created and are marketed by pediatricians.
The study, published Monday in the journal Pediatrics, tested the sound levels of 14 infant sound machines played at maximum volume at 30, 100, and 200 centimeters away from a machine that modeled a six month’s old ear canal. When placed at a 30 and 100 centimeter distances, all 14 machines exceeded 50 dBA, or decibels, which is the current recommended noise limit for infants in hospital nurseries. Thirteen of the machines exceeded the recommended noise limit even from 200 centimeters away.
Three of the machines were greater than 80 dBA, which, if played for more than eight hours, exceeds the recommended noise exposure even for adults and could lead to hearing loss or a delay in hearing development, the study found.
The suggestion that exposing infants to continuous white noise may delay their language and hearing development is based on previous studies done on rats. But common sense tells us that prolonged exposure to any one type of noise -- whether it's white noise, loudness, or even complete silence -- can't be healthy for babies' hearing development. Babies should be exposed to a variety of different sounds throughout the day, especially human voices. These exposures help normalize sound changes, so tiptoeing and complete silence won't be the only way they'll be able to snooze.
The study did not disclose the names of the machines they tested, and they didn’t study test the machine around actual infants. In general, there aren't many reported cases of infant hearing loss from white noise machines.
Still, the researchers recommended against using the maximum volume of the machines and keeping them more than 200 centimeters – or 6 1/2 feet – away from an infant. Many white noise machines don’t list the sound levels on the box, so it might be worth calling the product manufacturer before buying.
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