A group of small children sits cross-legged with their teacher, Steve Mejía-Menendez, on a round carpet. He's a pre-K teacher at Lee Montessori Public Charter School's campus in Southeast Washington, D.C., and although I'm here to meet him, I almost don't spot him because he's eye level with his students.

Mr. Steve, as he's known here, is talking a few students through a geometry lesson when another student approaches to ask an unrelated question. This kind of distraction happens all the time in classrooms around the United States. Mr. Steve doesn't lose focus. He uses American Sign Language to say "wait" — palms facing up, fingers wiggling — and the child waits quietly. When the lesson arrives at a natural stopping point, the student is invited to ask his question, and Mr. Steve silently responds by nodding his head along with his fist, which is sign language for "yes."

Blink, and you could miss the whole interaction.

This isn't a school for students with hearing disabilities, but Mr. Steve uses ASL as part of a broader approach to minimize noise in the classroom. And it's noticeably quiet. No one is talking louder than what's often referred to in Montessori schools as "the hum."

"Silence is kind of a peak achievement in a child's ability to control themselves," Mejía-Menendez says. "We create the conditions for children to concentrate."

Unlike this classroom, the city outside is full of noise. And studies show that too much noise, particularly loud noise, can hurt a child's cognitive development, notably for language-based skills such as reading. That's because if noise is just, well, noise, it distracts developing brains and makes it more difficult for children to concentrate. But when their environment is quiet enough for them to pay attention to sounds that are important or particularly interesting to them, it is a powerful teaching tool.

"[Young children's] brains are craving sound-to-meaning connections, so it's very important that the sounds around them be nourishing and meaningful," says Nina Kraus, a neurobiologist at Northwestern University.

She believes turning down the noise in our lives starts with embracing — even enjoying — silence.

Our noisy world shapes our brains

Silence is difficult to find and to create — for adults and kids alike. Around the world, fans of silence have begun to catalog the world's disappearing quiet places. But Lee Montessori is in Washington, D.C., a city that is surround-sound cacophony: busy highways, screeching commuter trains, jarring car horns, waterways with the blare of boat whistles and the seemingly constant whir of presidential and military helicopters and the drone of commercial airplanes.

But teachers do what they can. Inside this bright elementary school, there are no disruptive public address announcements. Students even wear special classroom shoes made of cloth and soft rubber soles.

"The hearing brain is vast," Kraus, the neurobiologist, says. "Our experience with sound really does shape us."

In fact, she has written an entire book about that topic, called Of Sound Mind. The brain processes auditory input faster than visual input, Kraus explains, and when we have the space to listen, our brains prioritize what we tune in to and reward paying attention through a release of dopamine.

For example, if you're a teenager excited to be learning the guitar, musical tones will get preferential treatment. If you're learning to play basketball, the bounce of the dribbling ball and your coach calling out plays will get your attention. There are certain sounds, like the sound of your own name, that your brain is unconsciously conditioned to respond to, even when you're asleep.

But when sounds are out of our control and not important to us, they shift into the category of noise: a neighbor's dog barking at a squirrel, a faulty car alarm, the drone of a highway.

When the sounds we are exposed to aren't helping us learn a new skill or stay safe at a busy intersection, the brain can get distracted and have trouble focusing.

It takes brainpower to ignore sound

When the world was a lot quieter, our brains paid attention to every little leaf rustle or snap of a twig as a tool for survival, Kraus explains. And when our brains are processing sounds that trigger questions like "Am I in trouble here?" or "Can I ignore this?", there is less room to focus on the task in front of us.

Consider a modern equivalent: When you're listening to someone tell you something and your phone dings — Ding! "Is that important?" — you just lost track of where you were.

Your brain has to work overtime to ignore sounds. Inside the cochlea — the spiral cavity of the inner ear that produces nerve impulses in response to sound vibrations — there are inner hair cells and outer hair cells that interact to amplify or deamplify the vibrations. Say you are listening to a piece of music on the radio, but traffic noise is in the background. Kraus says your brain will tell the outer hair cells to slow down and deamplify the traffic noise to protect your ears.

So when there is even just a moderate level of background noise, like traffic or a truck idling, our brains process more slowly. Kraus uses the analogy of a DJ sitting at a mixing board in your brain, assessing and adjusting sounds that come in all day long. The more that DJ has to do, the less operating power is available for your brain, making it harder to process new information.

It can become physically exhausting as well. People who have trouble hearing often experience listening fatigue.

Noise is especially distracting to young brains

"We can close our eyes, we can avert our gaze, but we hear in 360 degrees," says Emily Elliott, a psychology professor at Louisiana State University who studies memory and cognition and is one of the authors of a study about how auditory distraction affects a young child's ability to perform serial recall tasks. Elliott and her colleagues devised a test in which they gave young children a visual task of memorizing a series of items on a screen. Then they told the children that sounds would be playing but not to pay attention to them, because they weren't relevant.

"In general, performance goes down when you're asked to remember a series of things in order in the presence of irrelevant or distracting auditory stimuli," Elliott found. "So that tells us that [the sound is] somehow being processed in the cognitive system, because you can't just willfully go, 'I'm going to not listen.'"

Elliott and her team found that the critical ingredient of distraction is sound that changes in some noticeable way. "It could be music with lyrics," she says. "Music with lyrics is more distracting than music without lyrics."

They also found that children under age 7 in particular are bad at memorization because their brains are not yet able to employ a key tactic known as rehearsal. That's where you repeat things to yourself to remember them. And not only will they not remember a list of things, but they're also not aware that they won't remember them.

So when you're giving a young child directions or teaching a new topic and a distracting noise is present, the odds of the child remembering any of what you've told the child are pretty low.

One study of New York City schoolchildren in the 1970s found that students in classrooms next to noisy elevated train tracks performed significantly poorer on reading tests than their peers on the other side of the building. After the study was published, the city took steps to soundproof the classrooms and minimize the noise coming from the tracks, and a year later, the students' test scores were the same on both sides of the building.

In another study by neurologist Kraus and her team, they mapped the brain activity of 66 ninth-graders from Chicago Public Schools while asking them to perform reading and memory tasks. Then they monitored the children's electrical brain activity while watching a movie and listening to disruptive sounds. They found that the students who grew up under circumstances associated with noisier environments performed poorer on the reading and memory tasks and that those students had what she calls "noisier" brains — meaning a lot of neurons were firing all the time, even when the brain wasn't engaged in a task. You can think of that excess electrical activity as static.

"And if there's too much static, it makes it hard to make sense of all of the information that you want to be processing," Kraus says. According to Kraus, more static in a child's brain means it's harder for that child to listen and stay focused wherever they are.

How silence and some types of noise can benefit children

Kraus believes silence can be a benefit to children. When she and her team monitored kids with "noisy brains" under scalp electrodes, they found that periods of silence helped lessen the static.

Her team has also found that making meaningful sounds, like playing a musical instrument or singing, builds and strengthens neural connections.

Other research has found that pure silence can be healing. In one study on mice, scientists tracked brain cell growth among mice that were exposed to white noise, mice pup sounds, classical music and ambient sounds, and they compared those mice with mice that were left in silence. The mice that were left in silence had the most significant brain cell growth, leading researchers to conclude that the act of listening to silence regenerates nerve cells.

But absolute silence is rare outside a controlled lab environment. Even in the middle of the woods, you'll hear natural sounds of birdsong, the running water of a stream, leaves rustling and insects buzzing. These types of sounds could be described as noise, but they are calming to us. And if we try, we can find and re-create these natural sound environments in the middle of a city.

In addition to being a researcher, Elliott, the psychology professor, is also a mother of three. She learned early on as a parent to put white noise machines in her kids' bedrooms so that if one of them woke up screaming in the middle of the night, they didn't all wake up.

"White noise is fascinating because it masks lots of variability in sound," she says. "It takes out some of the frequency ranges and presents something that sounds like a continuous, steady sound." In other words, it mimics running water in a stream, and our brains tune it out.

This type of noise becomes a benefit in this situation, because it's masking the variability of the other sounds that would be a distraction.

Get cozy with the sounds of silence

Creating enough quiet to help hear meaningful sound is easier said than done. Some blame, in part, a culture that promotes constant stimulus. "There is some expectation that you need to be loud and flashy to capture your child's attention. Everything has to be a fun fair," says Ellen Doherty, chief creative officer for Fred Rogers Productions.

That's the company that inherited the mantle of Mister Rogers' Neighborhood, the children's television program developed in the 1960s and known for its calm and reassuring tone. It's still producing media for children, including Doherty's series of shorts, Through the Woods, which is deliberately quiet.

The three-minute shorts are about a kid walking through the woods, wondering, observing and experiencing. Instead of background music, you hear birds chirping, the wind blowing and leaves rustling. The sound designers do a believable job of making viewers feel like they are in the woods. But Doherty says this kind of programming goes against the grain of expectations.

"We take our shows to focus groups and ask parents, 'Would your child watch this?'" Doherty says. "And so often, parents say to us that if it's not bright and flashy, 'my kid won't watch that.'"

Doherty calls that type of show the fun fair. She believes you can have good shows with music and bright colors that aren't distracting but actually work to teach learning skills such as how to manage emotions or calm yourself down.

"My metric," says Doherty, "is does this need to exist?"

"I think that we need to be able to honor silence," Kraus says. "And there's something almost mystical there. You know, may we have a moment of silence? It's really a time to kind of get into yourself."

Using Doherty's question, "Does this need to exist?" as a guide, we might begin to think of silence as a chance to learn and look forward to making our lives quieter.

Edited by Emily Harris and Steve Drummond; visual design and development by LA Johnson; research by LA Johnson; fact-checked by Will Chase; copyedited by Preeti Aroon.