Infant Sleep Machines at Maximum Volume Reported as Hearing Risk

Sound devices used to lull infants to sleep can be loud enough at maximum volume to damage their hearing, researchers reported Monday. 

Researchers at the University of Toronto evaluated 14 popular sleep machines at maximum volume and found they produced between 68.8 to 92.9 decibels at 30 centimeters, about the distance one might be placed from an infant’s head. Three exceeded 85 decibels, the workplace safety limit for adults on an eight-hour shift for accumulated exposure (NIOSH). At 100 centimeters, all the machines tested were louder than the 50-decibel limit averaged over an hour set for hospital nurseries in 1999 by an expert panel concerned with improving newborn sleep and their speech intelligibility.

“Farther away is less dangerous, a lower volume is better and shorter durations of time, all things that deliver less sound pressure to the baby,” Dr. Papsin said. Yet some models are designed to be affixed to the crib.

A concern is whether listening to white noise can be detrimental to auditory development. A 2003 study (Science) found continuous white noise delayed development of the brain’s hearing center in newborn rats. In humans, the brain of a newborn is learning to differentiate sounds at different pitches even during sleep, said 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...they might not be as responsive as they otherwise should be to soft speech,” she said.

 (original article by Catherine Saint Louis from March 3, 2014 New York Times)