Whether you are sensitive to bumps in the night or sleep like a rock, sound has the potential to affect your rest and your health.
It's easy to overlook the significance of sensory cues during rest, as it can seem as though sleep makes us oblivious to the outside world.
However, think back and you can likely recall a time where a sudden sound woke you up or a noisy locale made it hard to doze off. In fact, temperature, smell, light, physical comfort and sound all have the potential to influence sleep according to recent research.
Sound appears to have both positive and negative influences, depending on types, noise level, personal preference and other factors. For example, gentle background noise can diffuse a noisy street, while a partner's snoring or creaky pipes can result in restless nights.
Read on to see how sound influences sleep in both the short-term and long-term, and how to optimize your environment for better nights.
The Effects of Sound During Sleep
Sounds that are trivial during the day can become bothersome at night, especially when they are abrupt. Even if you don't fully wake up, noises can arouse you slightly and affect sleep cycles. There are many potential sources of sleep stealing sounds, ranging from things in the home like appliances, televisions, pets and other people, as well as outside sounds like storms, traffic and urban city noise.
One research review published in the Noise & Health journal suggest studies show a link between nighttime environmental noise exposure and cardiovascular disease, and that even low-level noises may impact health due to sleep disturbance.
Environmental noise, from things like road traffic, trains, planes and wind turbines, is a significant policy issue for the World Health Organization. Research in Europe suggests that noise disturbance can cause real health side effects, and the WHO estimates Western Europeans lose 1 million years of healthy life due to traffic-related noise. Sounds as low as 30 decibels can affect rest, and by comparison, busy traffic comes it at 70 dB while a subway registers 90 dB and an airplane taking off comes in at 100 dB.
According to the WHO's Night Noise Guidelines, here's how noise levels affect sleep:
|Decibel Level||Sounds Like||Impact on Sleep|
|Under 30 db:||Normal breathing to a soft whisper, watch ticking, or a quiet library. A quiet rural area.||Little to no effect on sleep for most people.|
|30 to 40 db:||Whispers to a quiet room or office or bird calls. A quiet residential area.||Potential for awakening, body movements, arousals and sleep disturbance. Children, elderly and ill most vulnerable to side effects.|
|40 to 55 db:||A quiet room to moderate rainfall, a refrigerator or an air conditioner at 100 feet. A quiet suburb.||Health effects have been observed and noise at this level may affect most people.|
|Over 55 db:||Normal conversations, background music, washing machine and louder.||Considered a dangerous level for public health, increasing annoyance levels and sleep disturbances. Some evidence of increased cardiovascular disease risk.|
Sources: WHO's Night Noise Guidelines, American Speech-Language-Hearing Association
The intensity and severity at which noise impacts sleep is somewhat individual though, and some people are more sensitive than others. One study found that brain rhythms play a role in people's ability to tolerate noise. Generally, noises are most likely to wake people during stage 2 sleep, the light, non-REM cycle we spend about half the night in. Age also factors in, with studies showing children and elderly people to be most vulnerable to sound disruptions.
Emotional noises may perhaps be even more influential, with research showing evidence that mothers are easily woken up by their infants' movements and that a person's brain shows more activity to hearing their name than to beeps during sleep.
Over time, people can also become used to, or "habituated to," noises in their environments, resulting in reduced effect. One study found that people experienced fewer cortical arousals (changes in brain waves) on subsequent days when exposed to traffic sounds at night, however, cardiac arousals (heart rate) did not habituate during the study.
Using Sound to Your Advantage
Although much of the research focuses on learning about detrimental side effects of sound, it can have a positive affect on sleep as well. Sounds like white noise, for example, can moderate intermittent noise levels and provide a consistent backdrop for more peaceful rest.
Pediatric sleep consultant Jennifer Schindele suggests that environmental noise and new sounds can indeed disrupt sleep, however she finds that sound machines can help both kids and adults sleep well:
"I often find that the addition of low to moderate level white noise can be very helpful to the sleep of my young clients. White noise works to block out normal everyday environmental noises that could cause a person of any age to startle awake or keep them awake in the middle of the night where solid and consistent sleep is needed the most."
"Finding a good sound machine that offers white noise or gentle rain as sound options can help improve anyone's sleep. In fact, I often learn that the parents of the children I work with begin to use white noise in their own bedrooms to help improve the quality of their sleep. It is quite remarkable how one small change can make such an incredible difference in the ability of the human body to attain healthy sleep."
Dream Team Baby founders Conner Herman and Kira Ryan also express support for sound machines, particularly for establishing healthy sleep routines in children:
"When we are in lighter stages of sleep, sounds around us can more easily interfere with sleep. During these sleep stages, normal external noises, such as a phone ringing, a door slamming, or a dog barking, have a higher chance of waking us up. If you have a child who has a difficult time falling asleep, the last thing you want is for him or her to be woken prematurely."
"One way to use sound to your advantage is to play white noise the entire time your child is asleep. White noise will mask potentially troublesome external noises and help your child remain asleep longer. If used consistently, white noise also has another benefit. It can become a positive sleep cue. Your child will hear the noise at sleep time, associate it with sleep, and his or her body will involuntarily relax into sleep."
The idea of sound machines or white noise to condition external noises is supported by science, too. One team of researchers found white noise helped reduced awakenings to common intensive care unit sounds, by smoothing the difference between baseline and peaks in noise. An older study of infants found that 80 percent fell asleep within five minutes listening to white noise, compared to only 25 percent in the control group without noise.
Controlling Sounds In Your Environment
Sound and noise are a fact of life, and many types are simply unavoidable. However, there are a few helpful steps you can take to minimize noise pollution during rest and help your family sleep better.
If you notice that you wake up often during the night or you feel less than well-rested in the morning, consider tracking your sleep using an app like SleepBot or Smart Alarm Clock. Both of these apps and many others record any disruptions while you sleep, which can give you insight into noises that may be waking you up or disturbing your slumber.
Minimizing Inside Noises
- Use white noise to create a consistent gentle soundtrack if bumps in the night bother you. It can be particularly helpful for children whose bedtimes are generally earlier than their parents'. White noise can come from a fan, sound conditioner, white noise machine, air purifier or other soothing sound. However, be mindful of the volume especially for babies -- a white noise machine shouldn't be too loud. Experts vary, but below 50 to 65 decibels or so is considered maximum. For reference, that's similar to or quieter than a soft shower or normal conversation.
Minimizing Outside Noises
- Place your bed away from outside walls when possible.
Do you live in a noisy city? How do you notice sound impacting your sleep, or what best helps you sleep through the night?
This article originally appeared on the Amerisleep blog.
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