Silence is good for your brain and lowers stress, but where can you find it?

Follow me into the past for a moment. Imagine a fisherman waiting for a bite on his line while sitting in his boat off the Japanese coast 500 years ago; a woman crocheting lace in the early morning light during the late 1600s; a child watching his family's herd of goats on mountainside 1,000 years ago; or a Bronze-era farmer planting potatoes, rice or beans in dark, loamy soil. What do you hear? Not much, probably. Except for the small sounds of their work and some human conversation or singing, much of human history was mostly silent. Loud events, like a group of musicians performing together or the boom of a thunderclap, were rare.

As soon as there were cities, people and their animals crowded together, and the result was, of course, noise (and plenty of it). But most people didn't live in cities until recently, and the ability to produce sound through a speaker is even newer. Edison didn't invent the first phonograph until 1877, and it took several decades for them to become common. Today, music or other sounds projected through speakers are ubiquitous.

Loud and louder

It's gotten really loud out there — and constant noise is no longer confined to cityscapes. On my last two visits to national parks, I had to ask people to turn off their blaring phones. Not in a parking lot, but miles out in the wilderness on hiking trails that stopped off at scenic viewpoints — where some people felt compelled to blast music as they Instagrammed the view. Both times I suggested pretty tersely that many people, including myself, visit American's national parks for some peace and quiet. In both cases I felt incredibly frustrated: Why must we have noise everywhere?

I'm not the only one desperate for some quiet. MNN blogger Robin Shreeves works at home, and like me, is driven to distraction by the ear-splitting drone of leaf-blowers and lawnmowers. On some days, the noise sounds like it's coming from every angle. Case in point: While I wrote the intro to this article, there was a leafblower on the property to my left; now there's one at the house on the right. And it's summer, so there aren't any leaves to blow. My neighbors would rather use a blower to sweep a deck than a broom.

Even as the world gets noisier, scientists are learning more about the very real negative physical and mental effects of noise. We've known since the middle of the last century that constant noise is a stressor on the body. Studies have shown that it can cause or exacerbate hypertension and heart disease, cause sleep interruptions (which has its own negative health outcomes) and, naturally, lead to hearing loss if the sound is loud enough. And chronic noisy situations can lead to lower educational attainment for exposed kids.

Why silence really is golden

And it's through those studies of noise pollution that we are also getting a handle on how important silence is to the brain and mental health.

In 2006 physician Luciano Bernardini and his son, who were both amateur musicians, wanted to better understand what happened in people's brains when they listened to different types of music. In the experiment, 24 people listened to six different tracks and measurements were taken, including blood circulation in the brain, CO2 levels and blood pressure. Bernadini noticed that these measurements spiked with faster-tempo music and decreased with relaxing music. "During almost all sorts of music, there was a physiological change compatible with a condition of arousal," he told Nautilus. But most relaxing of all were the intervals between songs: the silence.

In this TedxBeaconStreet video, anthropologist and Tufts University assistant professor Nick Seaver discusses the time he and his wife spent 18 months in silence:

Duke University biologist Imke Kirste's experiment was a look into noise and neurological reactions to it. She was testing different sounds on mice to determine which ones might lead to new brain cell growth. Her control session was a 2-hour silent period, but when she looked at her results, she found that new cells were made by the hippocampus (the part of the brain in mammals that processes memory) during the periods of silence, not sound. "We saw that silence is really helping the new generated cells to differentiate into neurons and integrate into the system," Kirste told Inc. magazine of her 2015 study. Since some types of mental illness, like depression, are linked to a lack of new brain cells in the hippocampus, research into the connections between silence and mental health seems a logical next step.

A 2010 study by Michael Wehr at the University of Oregon also looked at sound versus silence in mice, and he found that the brain doesn't go to sleep during silent episodes, so it's not a simple "on" with sound, "off" with silence effect. In fact, the part of the brain that processes sound has a whole section of neurons that go off when silence starts, and is just as much of an "event" as when sound is heard. It's just another kind of event that leads to other activity. Like, for example, building new brain cells, as Kirste's research found.

All of this research into silence's impact on health outcomes and neurophysiological effects point to the very real benefits of quiet time. It also speaks to why we feel tired after flying in a jet for a few hours (the constant noise is exhausting) and to why most spiritual retreats are quiet and why some are even completely silent or include long stretches of silence. I've never heard of a raucous monastery, have you? Even in a non-religious setting, the popularity of silent retreats grows year over year as more of us realize we need a break. Our brains do different kinds of work when we are surrounded by silence, work that we are probably missing out on if we are constantly surrounded by noisy situations.

And yet, these days, that quiet time is being marketed as a luxury good, as John Biguenut points out in an article in The Atlantic. Biguenut details how silence costs serious cash, from quieter cars to chill airport lounges and how the poor disproportionately suffer from noise pollution that they don't necessarily benefit from otherwise, including noise from highways, airports and factories.

Blocking it out

So I'm taking action. In addition to expensive noise-canceling headphones, like those made by Bose and other companies that can even block out the drone of a plane's engine, there are other tech tools you can employ to take your quiet back.

One is a new device called Muzo (disclaimer: I supported this Kickstarter), a device that promises to fight sound vibration with vibration to create much quieter indoor spaces in cities. In addition to dampening sound, you can also play relaxing music and soudscapes of various types and even keep others from hearing your intimate conversations, depending on the setting.

Ear plugs can be a simple, easy way to block sounds out so you can get some shut-eye or simply read in peace. And when you need to replace them, there are low-noise dishwashers, washing machines and vacuums to purchase. You could also work to soundproof spaces in your house. You can check out how loud a restaurant is on Yelp, and choose a quieter one, like this Berkeley eatery that spent serious cash for a quieter atmosphere.

Or, you can always take a long hike to the middle of the wilderness, and enjoy listening to the sound of silence. I give you my permission to tell off anyone who comes hiking along behind you blaring music from their phone. Remind them of John Muir's admonition in a letter to his wife in 1888: "Only by going alone in silence, without baggage, can one truly get into the heart of the wilderness."