April 17, 2003 -- A new study suggests that exposing infants to continuous white noise -- commonly done to soothe infants or drown out other noises -- may delay hearing and possibly language development.
Investigators found that exposure to continuous, unpatterned sounds such as white noise delayed development of the brain's hearing center in young rats.
Unlike speech or music, white noise, such as radio static or an air conditioner's hum, is random sound with no distinguishable auditory pattern.
In their study, published April 18 in the journal Science, Edward Chang and colleague Michael Merzenich, PhD, exposed rat pups to continuous background white noise loud enough to mask normal environmental sounds, but not loud enough to damage their hearing. Development of the hearing region of the brain was compared with animals reared with normal environmental sounds.
The researchers found the rats exposed to the white noise showed a significant delay in development of the hearing center of the brain. And development in these rats did not catch up to the unexposed rats until they were three to four times older. Though hearing development was delayed, it did mature to normal adult levels once they were no longer exposed to the continuous background noise.
Ironically, white noise machines and CDs are sold for infants who are colicky or have trouble falling asleep.
Both Chang and Paula Tallal, PhD -- a researcher who was not involved in Chang's study -- say it is probably not a good idea to intentionally expose babies and infants to nonstop white noise, but they say everyday exposures are probably not harmful for most children.
"The message is not that your baby should not be near an air conditioner or fan," Tallal says. "Continuous exposure may have an impact in babies at risk for learning disorders, but you have to think about all the sound exposures that a baby is getting. If you happen to live in an environment that is noisier than normal, it is that much more important to spend a lot of time talking to your baby or reading to expose them to clear [hearing] signals."
Tallal tells WebMD that 10% to 20% of children have some problems discerning subtle acoustic differences between sounds, and these problems may manifest though delayed speech or learning development.
"We are already using this [white noise] research to better intervene in children who are struggling because their auditory systems process information in a fuzzy way," she says.