Rather than soothing baby and parents alike, infant sleep machines could actually pose a risk to hearing and auditory development, according to a Canadian research study recently published in the journal Pediatrics.
Investigators discovered that when played at maximum levels, some of these sleep machines actually exceeded acceptable noise limits recommended for infants by hospitals and could even risk hearing loss in some cases.
For the study, researchers purchased 14 devices to compare, which can be obtained on the Internet and at traditional retail stores throughout the U.S. and Canada. The machines tested produced 65 sounds, ranging from white noise to nature sounds. Each device was then tested at maximum volume and evaluated at various distances to simulate a machine either hanging on the side of a crib (about 12 inches), being next to a crib (about 40 inches) and being across the room (about 79 inches).
Special attachments were used on the microphones to simulate ear canals and adjustments made to estimate what a six-month old child would hear -- because of differences in ear canal anatomy than that of an adult. The ears of young children and infants will enhance the high frequency sounds more than adult ears, meaning that traditional estimates might actually under-estimate the hearing loss risk without adjustments being made.
When placed either in or next to the crib, all of the machines exceeded the 50 decibel (dB) noise limit hospitals use and recommend for infants. Three of the machines produced levels greater than 85 dB hanging on the side of the crib -- levels that could actually cause permanent hearing loss if played consistently for eight hours.
Outside of risking a possible hearing loss, experts also warn that auditory development could also be at risk. If outside environmental noise is continuously drowned out by a machine, children may not be learning about sounds in their environment during the early stages of brain development. The long-term effects of constantly masking environmental noise at such an early age remains unknown.
Despite the many proclaimed benefits and recommendations for infant noise machines on parenting websites and magazines, the results of the study have audiologists, pediatricians and many other health care professionals concerned. As a result from the study, researchers and other experts suggest manufacturers include warnings on all infant sleep machines and consider recommendations to restrict the maximum allowed output of these devices. They also recommend all sleep devices include automatic shut-off timer.
While they aren't calling on parents to get rid of these machines completely, they do recommend that parents keep sleep machines as far away from infants as possible and set the volume to its lowest setting. They also suggest parents only use devices with automatic shut-offs or turn the device off once the child has fallen asleep.
-- Original publication: http://pediatrics.aappublications.org/content/early/2014/02/25/peds.2013-3617.abstract
Signs of childhood hearing loss:
Newborn (Birth to 6 Months)
-- Does not startle, move, cry or react in any way to unexpected loud noises.
-- Does not awaken to loud noises.
-- Does not freely imitate sound.
-- Cannot be soothed by voice alone.
-- Does not turn his/her head in the direction of your voice.
-- Does not point to familiar persons or objects when asked.
-- Does not babble, or babbling has stopped.
-- By 12 months does not understand simple phrases by listening alone, such as "wave bye-bye," or "clap hands." Infant (3 months to 2 years)
-- Does not accurately turn in the direction of a soft voice on the first call.
-- Is not alert to environmental sounds.
-- Does not respond on first call.
-- Does not respond to sounds or does not locate where sound is coming from.
-- Does not begin to imitate and use simple words for familiar people and things around the home.
-- Does not sound like or use speech like other children of similar age.
-- Does not listen to TV at a normal volume.
-- Does not show consistent growth in the understanding and the use of words.
If you have concerns your child may have hearing loss, discuss your concerns with your doctor and seek the services of a licensed audiologist. Children of any age can be professionally tested.
-- Dr. Kevin Liebe is an audiologist at Columbia Basin Hearing Center (www.ColumbiaBasinHearing.com) and serves as President-Elect of the Washington State Academy of Audiology.