If a so-called white noise machine is kept at full volume in
a room with a sleeping baby, it may be potentially hazardous to the child's
hearing, suggests a new study.
machine helps children with sleep apnoea
The study cannot say exposure to the machines' noise is
actually impairing children's hearing – just that the devices may be capable of
creating sounds loud enough to cause hearing
loss after prolonged exposure.
The report's lead author from the Hospital for Sick Children
in Toronto told Reuters Health that people should consider sound in terms of
dose. "Everyone knows aspirin
is safe, but everyone knows you don't take 40 of them," Dr Blake Papsin
White noise machines, also known as sleep machines, produce
sounds to soothe infants to sleep and help mask other noises, Papsin and his
colleagues write in the journal Paediatrics. But noise can cause hearing loss
at certain levels, and the ears of young children are different from adult
ears. Higher-frequency sounds get amplified by their smaller ear
The researchers write that the Canadian Centre for
Occupational Health and Safety and US National Institute for Occupational
Safety and Health recommend adults limit workplace sound exposure to no more
than 85 A-weighted decibels (dBA) for eight hours.
That's equivalent to a garbage disposal or blender operating
about three feet away. For young children in hospitals, it has been recommended
that they not be exposed to more than 50 dBA averaged over an hour. That's
equivalent to a
dishwasher running in the next room.
For the study, the researchers bought 14 different types of
white noise machines off the internet and in traditional brick-and-mortar
The machines produced a total of 65 different sounds that
included white noise and nature, mechanical and heartbeat sounds. Using a sound
booth, the researchers tested each device turned to its maximum volume and
placed sound meters at varying distances to simulate the machine hanging on the
side of a crib, being placed next to a crib and being across the room.
The microphones for the sound meters were fixed with special
attachments to simulate ear canals. The measurements were also adjusted to
estimate what a six-month-old child would hear.
Three machines were capable of producing noise in excess of
85 dBA when positioned on the side of the crib. All machines were capable of
producing sounds greater than 50 dBA when placed either in or next to the crib.
And all but one of the machines was capable of producing sounds greater than 50
dBA from across the room.
"The main message is that off-the-rack machines – three
of them – at certain conditions are capable of producing hazardous levels of
sounds," Papsin said.
"I'm not saying
they were (producing hazardous sound), but they were capable." Based on
their results, he and his colleagues suggest that parents place the machines as
far away from infants as possible and set the volume as low as possible.
They also recommend that parents limit how long the devices
are switched on. For example, they could have an automatic shut-off or turn the device
off once the child falls asleep.
Alison Grimes said she agreed with the researchers'
conclusions. Grimes, the head of audiology and newborn hearing at the
University of California, Los Angeles Medical Centre, was not involved with the
new study. "I think their recommendations are very appropriate with their
caution," she told Reuters Health.
"I think the other question to ask is what is the noise
in the environment that needs to be mitigated in this way?" Grimes said
children may not be able to learn about the sounds in their environment if they
are drowned out by a white noise machine. "Infants are designed to hear
speech and environmental sounds," she said. "That's how they do their
environmental learning." A representative from Graco, a maker of baby accessories
including sound machines, said the company didn't have a comment on the new
Papsin said he's not recommending that parents get rid of
their machines."That would be foolish," he said. "Parenting is
like juggling . . . I just gave the parents another ball."
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