The adage, “never wake a sleeping baby” is practically a mantra for parents of infants. Parents seeking peaceful nights are increasingly using sleep machines to mask excess noise that might wake a sleeping child.
However, a study published in the journal Pediatrics found that these machines can actually cause hearing loss and other health issues in infants.
Background Information
The US National Institute for Occupational Safety and Health (OSHA) has recommended a work-place noise limit of 85 A-weighted dB (dBA) for an 8-hour exposure for adults. Exposures above this could cause noise-induced hearing loss.
Due to the properties of the smaller infant ear canal, high-frequency sounds are amplified in the canal. Thus, a 50-dBA noise level over one hour is recommended as a maximum safe exposure for infants in hospital nurseries and NICUs.
Sleep machines, or ISMs, are designed to provide ambient noise to soothe an infant during sleep or to mask disturbing environmental sounds by producing louder sounds, thus preventing arousal from sleep.
They’re designed to be placed near or on a crib, and many web sites encourage parents to have the volume at a level that is equal to an infant’s cry. According to the American Tinnitus Association a screaming child can reach 110 dBs. Some manufacturers also suggest having them on continuously while the infant sleeps.
Study Findings
Noise exposure in infants can have detrimental effects on their physiologic state, in addition to their hearing development. Tachycardia has been measured in both term and pre-term infants after pulsed or continuous noise simulation.
With this in mind, researchers analyzed the maximum noise level of 14 ISMs that are widely available in the US and Canada. They combined for 65 total sounds including white noise, nature sounds, and mechanical sounds. Measurements were taken using a sound level meter in a sound booth.
The sounds were measured at 30 cm (simulating the machine on/in the crib), 100 cm (placement near the crib), and 200 cm (placement across the room from the crib). The average output levels at each distance were 79.1 dBA, 70.5 dBA, and 63.3 dBA, respectively.
All but one device was capable of producing noise above 50 dBA at even the furthest distance. The loudest machine recorded a 92.9 dBA at 30 cm.
Researchers also expressed concerns regarding white noise, as it has been shown that continuous white noise exposure in early development can alter the processing of sound intensity and alter behavioral development. It lacks the normal variations in frequency and intensity found in normal auditory output, resulting in a loss of organized representation of frequency in the brain.
Study Recommendations
Researchers hope their study will encourage manufacturers to better safeguard ISMs in the future. They recommend manufacturers:
- Limit the maximum output level.
- Print warnings about noise-induced hearing loss on packaging.
- Include a mandatory timer on devices marketed primarily for infants that would shut the device off after a certain amount of time.
In the meantime, researchers recognized that there are many parents who don’t want to stop using sleep machines, and recommend ways to minimize detrimental effects.
- Most sleep machines contain volume controls. Keep the sleep machine on its lowest volume.
- Place the sleep machine as far away from the crib as you can. Do not put it on the crib rail or in the crib.
- Operate the sleep machine for only a short amount of time, not the entire time the infant is sleeping.
Do you use or recommend sleep machines for infants? Will you change your habits after learning about the potential effects? We’d love to see some discussion in our comments section and also inside Sermo. Please join us here or inside if you’re an M.D. or D.O.
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