Tuesday, September 20, 2011

White Noise and Infant Hearing

A few weeks ago we wrote a post about hearing in our babies' senses series. For today’s post we are going to answer a reader question about white noise. Here is the comment we received:

“Do you know very much about the effects of white noise on babies? I've heard that it can slow down their hearing development? There are so many devices [white noise machines] sold though, and not much mentioned. We've been using it in our room with our 4 month old for at least 2 months now and just read that. I tried to do some research, and only found one study on some mice in the 90's.”

After reviewing the literature, we also could not find studies showing that white noise is harmful for human infants. The one study we did see was very small and tested the effects of continuous (24 hours per day from day 7 of life) white noise on rat pups (baby rats). Continuous exposure to white noise (70 decibels) was found to cause delayed development of the auditory cortex, an important structure in processing speech sounds. However, it’s important to note that the results of this study cannot be inferred to human infants exposed to white noise during a particular time of day. Why? Not only do human infants develop differently than rat pups, but this study only looked at non-stop exposure to white noise, not short term exposure during naptime or nighttime sleep. Common sense tells us that babies need to hear more than white noise. Some low-level white noise is safe for babies as long as it is not continuous and they are exposed to lots of different sounds throughout the day, especially human voices. Talking and reading to your baby every day is a great way to ensure proper development of your baby’s hearing.

Safe Hearing for Infants
Decibels (dB) are the measurement of the loudness of sounds. How loud the noise is plus the length of exposure to the sound determines the amount of damage to your hearing. The American Academy of Pediatrics and the National Campaign for Hearing Health states 85 dB is the threshold for dangerous levels of noise. Sounds less than this are unlikely to cause hearing loss. However, it’s also important to think about the cumulative exposure to noise over the course of a day. To give you an idea of what 85 decibels sounds like, here are a few everyday sounds and their decibel levels:

Normal conversation: 60 dB
Vacuum cleaner: 70 dB
Restaurants: 80-96 dB
Noisy toys: 90 dB (you can look for a noise rating on the package when you buy the toy or call the manufacturer to request this information)

What about White Noise Machines?
Most of the white noise machines I came across online operated at a safe level of about 60 dB. However, we recommend checking the decibel level before buying one to be sure that it is indeed at a safe level. If you can’t find this information online, call the product manufacturer.

Benefits of White Noise for Parents
In a past post about helping parents of infants get a little more sleep, we shared results of a study suggesting that white noise can be beneficial for parents as well. Healthy sleeping newborns can be pretty noisy because they move and make noises while they sleep. Since it’s best for babies to sleep in the same room as their parents, playing some low-level white noise can help you sleep through the wiggles and soft squeals your baby makes. By keeping the white noise low-level, you will still be able to hear your baby if she needs your help.
Please let us know if you have any other questions or comments about past blog topics. We love to hear from you!

References and Resources
Chang EF, Merzenich MM. Environmental Noise Retards Auditory Cortical Development. Science. 2003; 300: 498.

The Children’s Hearing Institute: http://www.childrenshearing.org/custom/hearing_health.html

1 comment:

  1. you can download free Db meters on most smartphone platforms too.

    And fans make GREAT white noise machines. And keep the air circulating and cool you off in the insane heat of summer.