White Noise: What We Know About Hearing and Language Development
There's been a lot of "noise" about whether white noise machines cause changes in the brain that lead to communication/language delays and learning disabilities. Let's break down what we know, and what we don't know.
First, we know that white noise machines can be loud.
Too loud to be used safely. A 2014 study by Dr. Sarah Hugh and colleagues in Pediatrics showed that 14 of 14 machines they tested exceeded 45 dB, the recommended maximum decibels in hospital nurseries. Three of the machines exceeded 85 dB, higher than what is considered safe for adults who are continually exposed without (such as in certain work conditions).
Second, we know that noise changes the brain.
It's worth pointing out that almost everything in the environment can change the brain. Your voice, your touch, the sights and smells in the room all change your baby's brain. What we want to create are conditions that change the brain in positive ways, or that give young brains what they need environmentally to grow and develop well.
In a 2017 study by Selehi et al, rats were exposed to 2 hours of 90 decibel sound in utero and in the newborn (critical development) period. There were changes in the central auditory system of the brain.
And because rats and humans are similar in a lot of ways, and because the central auditory system is responsible for processing sound for developing language and for learning, there are some concerns about what this means for human babies' ability to learn language.
No studies that I am aware of have been done to explore this further, so it is a question mark at this point.
Third, we know that many changes to the environment are not neutral.
Things we do can be positive, negative, and both. White noise machines probably do both: studies show babies can fall asleep faster AND show that noise can cause hearing loss AND that the hearing centre in the brain can be impacted. If white noise machines are on all the time, or reduce the language-richness of an environment (are we less likely to coo, or sing, or talk to our babies when white noise machines are on?), there may be a negative impact. But we don't know yet. It's speculation.
Fourth, we know that white noise machines aren't part of the "biological expectation" babies have of their environment.
We are adding something to get newborns to sleep faster and longer, even if biologically they aren't "supposed to" --babies need to wake up often and need support to fall asleep. For more on that, see last week's blog, “White Noise: What is it good for?”.
Last, most of the discussion on the risks of white noise machines aren’t about older babies. Using white noise machines to reduce sleep disruption in noisy households or with highly sensitive older babies may make a big difference in a family's "sleep plan". We just don't have any research exploring the pros and cons directly with older babies and young children.
So how does this all pull together to help you guide a decision around white noise machines? Here are seven things you can do that are evidence-informed:
Test your noise machine. (There's an app for that!). Make sure noise levels are 45 decibels or lower.
Keep sound machines at least 2 metres from your baby’s sleep surface. This is based on AAP measurements of decibel levels of white noise machines at 30cm, 100cm, and 2 metres away.
Keep sound machine below its highest volume. This helps support keeping decibels at a safe level.
Consider not using noise machines until after 6 months of age, especially if your baby is solo-sleeping (in Canada, room sharing is recommended until 6 months of age or beyon). Although this age is an arbitrary suggestion not based on research, 6 months is when SIDS risk has dropped significantly, and when sleep and body regulation have had several months to mature as well as on wanting to reduce the impact of environmental noise on the developing brain. This ensures that very young babies are exposed to the environmental noises that rouse them and regulate them (yup, as difficult as it is, babies are supposed to wake up often). The hearing centre in the brain continues to develop long after 6 months, but newborns are considered to be in a critical period for this development.
Limit its use. Use it only to fall asleep, or only while sleeping -turn it off when awake. AAP recommends limiting use to a "short period of time" but they don't specify what that means. This may ensure that white noise machines don’t impact the environment in other ways (like how much you talk to your infant, read to them, or coo to them).
Stop using it if it doesn't "work" for you (however you define it). There is no evidence that noise machines are a "negative" association -it's simply an association. If it works, and can be used safely, carry on. If reliance on it becomes a challenge (it breaks, you spend time away without it, etc), then gradually replace it with other sleep associations, just as you would with any sleep association that has outlived its usefulness to you and your baby.
If it doesn't work, rest assured, sleep development happens over time, and a white noise machine is only one strategy of many to support sleep.
So, I’m curious: do you use a white machine? And does the above information impact how you will use one?
PS: what's all the buzz about pink noise? Pink noise has a consistent "energy" level: it balances out frequency of the signal power and spectral density so that the total is always the same (as frequency goes up, spectral density goes down). This is firmly outside of my area of study, but apparently it can be a more pleasant sound for some people.
At the time of this article, there are no research studies on whether this is "better" or "safer" but you can explore whether you enjoy the sound of it more than static or white noise. At this point it is a preference thing, and not much more.