Knit Blog

You’ve been hearing the recommendation since your child was a baby: try white noise. It seems counterintuitive - can loud noise really help your child sleep better? It can, but the way it works may be different from you think. Here’s what you need to know about white noise, how it works, and how to choose the best background noise for your child’s nighttime slumbers.

How White Noise Works

The basic concept of white noise is simple. There’s nothing magic about the noise itself; what it does is mask ambient noise. Sudden sounds - like a creaking stair, or you laughing at your spouse’s jokes - are likely to wake your child because they’re sudden. It’s the change in noise level that triggers arousal and can wake your child up. An ongoing, unchanging, background sound can solve that: because the sound stays consistent, it doesn’t cause arousal.

From a biological perspective, it makes sense for humans to wake up when something changes. You know the environment was safe when you fell asleep, so if something changes, it could be a sign of danger. Sudden noises - or any sudden environmental changes - trigger arousal as a safety measure: a sudden change could mean a threat, so you need to wake up and make sure that you’re still safe. White noise helps your child’s brain know that nothing in her environment has changed, so it’s safe to stay asleep.

Concerns About White Noise

White noise doesn’t improve sleep for everyone, but it’s unlikely to make sleep worse. But there is one danger that some experts have brought up, which is the danger of high decibels of noise - to a level that’s so loud it could damage hearing. This is more of a concern for babies than for older children, since your child can adjust the noise level herself so it feels comfortable, and she’ll notice if it’s loud enough to hurt her ears. But if you turn the volume all the way up on your white noise machine, you could be setting the sound at a level that can damage hearing. Some can be as loud as 85 decibels, especially if you place them right next to your child’s head - as loud as an idling bulldozer. In the workplace, federal regulations require protections for adults who are exposed continuously to 85 decibels of sound or more, and children may be more vulnerable to noise exposure.

Playing white noise at the top volume of your app or machine could potentially harm your child’s hearing, so be cautious. Let your child choose the level of sound that is soothing for her, and test it by standing at the same distance your child is from the sound to see if it hurts your ears. Dangerously loud sounds will feel painful, so if you feel comfortable, it’s probably okay for your child too. If you’re unsure, you can test the sound level with a decibel meter.

What Type of Background Noise Is Best?

White noise can be as simple as turning on a fan in the room - anything that provides a continuous sound that’s loud enough to mask other noises. However, if you try to get any more complicated with your white noise, you’ll soon discover there are a lot of options. White noise is just one choice - there’s a whole rainbow of sound colors, from pink and blue noise to Brown (which is named after a person, not the color). Plus there are ambient nature sounds like thunderstorms, falling rain, chirping birds, and rushing wind. What’s the best option for your child’s sleep?

What do the different “colors” of sound mean? Similar to light wavelengths, the colors refer to different frequencies of sound. White noise is the name for sound that’s evenly distributed across all the frequencies that humans can hear. It’s a chaotic combination of every sound audible to the human ear, all playing at the same volume together. This creates an even blur of static that does a great job at masking sound, but can feel irritating to some people because the higher level frequencies can sound shrill.

Pink noise is more soothing for many people because it lowers the level of the higher frequencies and raises the volume on the lower frequencies. This sound is more similar to sounds found in nature, and several studies indicate that it’s more effective for sleep, including a 2012 study that showed it increased deep sleep time both at night and while napping, and a 2013 study that showed pink noise at night improved both sleep and memory. However, most of these studies compared pink noise to silence, not to white noise, so that won’t help you when you’re trying to choose which color to play in your child’s bedroom at night.

And if pink noise is great, Brown noise may be better - it turns the lower frequencies up even higher, giving a deeper and possibly even more soothing sound. Blue noise, on the other hand, does the opposite - it turns up the volume on the higher frequencies, creating a more shrill, hissing sound. For most people, this is less soothing than lower frequencies.

Finally, of course, there are ambient nature sounds like thunderstorms. There’s very little research on how these compare to static noise of any color, but plenty of people use it to sleep.

So which type of noise is right for your child? The likely answer is: science doesn’t know, but your child probably does. Any type of ambient noise will help mask sudden sounds, which is the main purpose of white noise, so the best type of white noise is the one that sounds best to your child. Let your child experiment with different sounds and see which one feels most relaxing to her - which might even be the sound of silence.