Some parents use "infant sleep machines" to mask environmental noises in busy households and help their babies get to sleep. But a new study finds that these machines can also contribute to hearing loss in babies.
Any parent knows how difficult it is to get a baby to sleep and to stay asleep. Babies are easily disturbed by everyday noises, and a lack of sleep can have adverse physical consequences not only for the child, but for their parents.
Sleep machines are devices designed to help babies sleep more soundly. They are placed next to the baby's crib and work by generating ambient noise that masks other noises from around the house or outside that could disturb the baby.
Websites that proclaim the benefits of infant sleep machines often suggest that parents and childminders should have the device on continually while a child is sleeping. A common recommendation is that the volume of the sounds played by the machine should be equal to or louder than the cry of an infant.
But it is common knowledge that being exposed to noise at high output levels can cause hearing loss. This is why there are regulations in adult workplaces that set precise limits on how much noise workers can be exposed to. The US National Institute for Occupational Safety and Health recommend a limit of 85 "A-weighted decibels" (dBA) for an 8-hour exposure.
As infants are still developing and have much smaller ear canals than adults, it is possible that babies are more susceptible to the adverse effects of noise levels than adults. Therefore, a noise level limit of 50 dBA averaged over an hour is recommended for hospital nurseries.
With this in mind, the researchers behind the new study - published in the journal Pediatrics - set about investigating if the noise from infant sleep machines crosses into harmful output levels.
Infant sleep machines produced noise levels in excess of adult exposure limits
The researchers tested all 14 sleep machines that are currently available to buy in North America. These machines offered a variety of different sounds, including white noise, nature sounds, mechanical sounds and heartbeat sounds.
Researchers found that "infant sleep machines" - used to drown out noises so babies can get to sleep - may be putting infants at risk of hearing loss.
They found that, at maximum volume, the devices had a mean average of 79.1 dBA. However, three of the sleep machines produced outputs of greater than 85 dBA - even louder than the noise limits of adult workplaces. And the loudest sleep machine could produce a maximum noise output of 92.9 dBA.
From their results, the researchers conclude that infants exposed to sleep machines could be at risk of hearing loss or of their auditory systems not developing properly.
The researchers think that safe use of these devices could be possible, but only with policy recommendations that set appropriate limits on the manufacture and use of the devices.
The researchers make three policy recommendations for manufacture of sleep machines:
- Manufacturers should be required to limit the maximum output level of sleep machines
- Manufacturers should be required to print warnings about noise-induced hearing loss on their products' packaging
- Manufacturers should be required to include a timer that automatically shuts the device off after a predetermined period of time.
They also make the following recommendations that families using infant sleep machines should follow:
- Place the device as far away as possible from the baby, and never in the crib or on the rail of the crib
- Play the sleep machine at a low volume
- Play the sleep machine for a short duration of time.
Medical News Today reported in 2012 on approved techniques used in "infant sleep training."