Though they might quash sleepless nights for parents and children alike, emerging research suggests that the hum emitted by sound machines could be detrimental to infants' hearing.
In a recent study, entitled Infant Sleep Machines and Hazardous Sound Pressure Levels, Canadian researchers investigated potential risks associated with sound machines. The study looked at 14 different machines, purchased online and at bricks and mortar stores, to determine the maximum sound levels. While the study didn't set out to gauge the effect on children's hearing, it nevertheless found that some machines, at their loudest, exceeded safety recommendations for adults' noise exposure - suggesting that children's hearing, still undergoing crucial developmental stages, would be more severely impacted. Smaller ear canals amplify higher frequencies, meaning that children's ears are more susceptible to damage. "These machines are capable of delivering enough of a dose over a period of time to theoretically cause hearing loss, but that's not been tested," cautioned Dr. Blake Papsin, who led the study.
Occupational health and safety officials have noted that a workplace limit capped at 85 decibels over eight hours is the recommended noise level for adults. However, three of the tested machines (all brands and models remain undisclosed) had maximum volumes over 85 decibels, and if played over the course of a night, could likely mar an infant's auditory advancement. As a ballpark figure, children's hospitals and neonatal wards maintain sound levels at a maximum of 50 decibels averaged over the course of an hour, or roughly the same volume as a dishwasher operating in a neighboring room.
Nevertheless, the team advised that such machines could be used safely, provided that the volume doesn't exceed recommended levels, the sound is only played for a short time, and that the machines are placed a sufficient distance from the child. "The main message is that off-the-rack machines - three of them - at certain conditions are capable of producing hazardous levels of sounds," said Dr. Papsin. "I'm not saying they were (producing hazardous sound), but they were capable."
As such, the study recommended that manufacturers adjust the maximum volume on the devices while issuing print warnings on the packaging. The researchers also advised that the manufacturers develop an automatic timer to switch off the machine when it's run for an appropriate length of time, thus eliminating the risk of prolonged exposure.
Also of note is the risk of developing hearing loss later in life, with studies in animals demonstrating a possible link between age-related hearing conditions to early exposure to noise.
