(RxWiki News) Crickets, ocean waves, trains, heartbeat, wind, white noise… these are just a few sounds available in infant noise machines. But how wise is it to use these while babies sleep?
A recent study found that baby noise machines sold to help infants sleep can reach potentially dangerously high volumes.
All the machines tested by a group of researchers were able to reach volumes that were capable of causing hearing damage even in adults if played too close for too long.
These researchers expressed concerns as well about the impact of playing continuous white noise for babies.
"Use noise machines at low volumes and sparingly."
This study, led by Sarah C. Hugh, MD, of the Department of Otolaryngology at the University of Toronto, looked at the volume levels on various white noise machines that may be played around babies.
Dr. Hugh and colleagues wanted to learn whether these machines' volumes reached levels that may actually be harmful for infants' hearing development.
Infant sleep machines, or white noise machines, provide ambient noise or a sort of "dull roar" that can cover up other sounds in the room where a baby sleeps.
The researchers tested 14 different infant sleep machines while they were played at maximum volume.
The machines each played anywhere from one to 10 different types of noises, ranging from white noise to nature sounds (wind, rain, birds, etc.) to mechanical sounds (traffic, trains, etc.) to a heartbeat sound.
The machines were tested at 30 cm, 100 cm and 200 cm away from the device that measured their decibel levels, and the researchers made calculations to account for the volume that would reach a typical 6-month-old's ear canal.
At 30 cm away from the measuring device, the maximum volume on all the devices was greater than 50 A-weighted decibels — the maximum recommended volume for hospital nurseries.
For sound machines placed 30 cm away, roughly equivalent to a machine on a crib rail, the decibels ranged from 65 to 95.
For those placed 100 cm away, roughly equivalent to sitting beside a crib, the decibel levels at full volume ranged from 60 to 85.
Finally, at 200 cm away, roughly equivalent to the machine sitting across the room from a crib, the highest volume ranged from 45 to 80 decibels.
In fact, even at that distance, similar to having a noise machine at full volume across the room from a child, all but one of the machines exceeded 50 decibels.
Three of the machines reached volumes measured at more than 85 A-weighted decibels when only 30 cm away.
This volume level, if played for more than eight hours, would exceed the current occupational limits for fully grown adults's cumulative noise exposure in the workplace.
Such a high volume played for that long could lead to hearing loss in even a fully grown adult.
The researchers said that placing infant noise machines 200 cm away from a child and played at lower than full volume should help reduce the risk of hearing loss and come closer to a "safe" distance.
However, they still expressed concerns about continuous use of noise since babies' hearing is still developing.
"Exposing infants to continuous white noise is particularly concerning given that white noise, unlike speech which varies in frequency and intensity rapidly over time, has an almost constant intensity across a range of frequencies," they wrote.
"Evidence in neonatal rats shows that the normal frequency map in the primary auditory brain is severely disrupted by continuous white noise exposure," they wrote.
These researchers acknowledged that their study could not provide insights into how infant noise machines are actually used in everyday life, but they expressed concern about the products' lacking instructions in safe use.
Thomas Seman, MD, a pediatrician at North Shore Pediatrics in Danvers, Mass., said he does not usually recommend white noise machines except when a child has colic since studies have shown that noise machines help with children who have colic.
However, he offered some general guidelines for parents who do use them.
"When using the machines for this I typically recommend parents turn the volume up until the child hears it, and then to turn it down to the absolute lowest" that is still audible, he said.
"This is to be used until the child falls asleep and can then be turned off," Dr. Seman added. "Most often, I help parents understand that the fussiness is usually a result of other issues and often parental anxiety that their child is in some form of severe distress and that they should not cry."
This study was published March 3 in the journal Pediatrics. The research did not use outside funding, and the authors reported no conflicts of interest.