The way in which our brains interpret the noises we hear as either non-threats or threats, may explain why the sounds of water help us fall asleep.
Orfeu Buxton, an associate professor of biobehavioral health at Pennsylvania State University, said that sounds of non-threats, like the waves crashing ashore or the wind blowing through the trees, work to calm people down.
The character of the sound, which can activate the threat-activated vigilance system in the brain, is even more important than its volume. The threat-activated vigilance system can be defined as a protective mechanism that helps us make a distinction between dangerous situations. According to Buxton, since the noise information is processed by the brain, the type of noise you hear defines whether you will wake up or not.
In 2012, Buxton conducted a study in a hospital setting on the distinction between gradual non-threat (crashing waves) and abrupt threat (like scream or shout).
For instance, even when they were set at volumes of forty decibels – which would equate to the sound that a whisper makes – alarms from hospital equipments made fifty percent of the study participants wake up from deep sleep, and ninety percent from shallow sleep. An explanation would be that alarms – regardless of their volume – are sudden noises.
However, the sounds of traffic or a helicopter did not wake the study participants as often as ringing phones and alarms, even when reaching volumes around seventy decibels – equivalent to a shout. People are more inclined to respond to noises that come out of nowhere, because they might indicate the presence of a threat, according to Buxton.
When they are relatively loud, non-threatening noise are also able to mask sounds that might raise red flags in the threat-activated vigilance system, Buxton said. That could be the reason why water-themed sleep aids have become so popular in recent years, ranging from cassettes to CDs to MP3 players to the apps that we use nowadays.
That being said, Buxton advises people with insomnia not to rely so much on their mobile devices for sleep. That is because phones can be terrible at keeping quiet, and that every beep, update, or other things of that nature are very likely to interrupt ones sleep.
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