How Listening to Silence Changes Our Brains

Yout’s not just your imagination. The world is literally louder right now than it’s been at any time in known history.

Even though COVID shelter in place orders caused a temporary drop in decibel levels in the short-term, modern life is still omnipresent: More cars, more helicopters and buzzing drones. Since emergency vehicles must be loud enough that they can cut through all the noises around them, decibels from their sirens provide a measure of how loud our landscapes really are. Today’s sirens are an estimated six times louder than they were a century ago, indicating that our population centers are vastly louder, too. According to the National Park Service’s Natural Sounds and Night Skies Division, noise pollution doubles or triples every three decades.

Are all these sounds just annoying?

Oder, do we sacrifice something for our bodies and minds if we allow silence to slip?

Across disciplines—from neuroscience to psychology to cardiology—there’s growing consensus that noise is a serious threat to our health and cognition. And that silence is something truly vital—particularly for the brain.

“Noises cause stress, especially if we have little or no control over them,” explains Mathias Basner, a professor at the University of Pennsylvania who specializes in sound processing and rest. “The body will excrete stress hormones like adrenaline and cortisol that lead to changes in the composition of our blood—and of our blood vessels, which actually have been shown to be stiffer after a single night of noise exposure,” Basner says.

The sound waves that hit the eardrums vibrate bones and cause vibrations in fluids. These ripples create waves in the fluids within the cavity, which is a small, spiral-shaped hollow called the cochlea. The cochlea’s tiny hair-like structures convert sound waves into electrical signals that the auditory nerve sends to the brain. Neuroscientists have found that these signals go to the amygdalae, the two almond-shaped clusters of neurons that form the primary biological basis of our emotional lives—including our fight-or-flight response. The process by which stress hormones are secreted begins when signals reach the amygdalae. Too many stimuli result in excessive stress—as evidenced by the presence of chemicals like cortisol in our blood.

In 1859, reflecting on her experiences with patients in a hospital during the Crimean War, the legendary British nurse and public health innovator Florence Nightingale wrote that: “Unnecessary noise, then, is the most cruel absence of care which can be inflicted either on sick or well.” The latest research demonstrates that she had an essential point.

For years, the concern has been that excessive noise can cause hearing loss—a grave issue that can also lead to social isolation and loneliness. Over the last few decades, a wide range of peer-reviewed papers has shown that there are risks to cardiovascular disease, stroke and depression as well as other complications.

Arline Bronzaft was a pioneering environmental psychologist who discovered in 1970 that Manhattan middle schoolers who lived near elevated subway tracks were more likely to fail reading tests than students in calmer schools on the other side. Since the stress response to noise is well established, it was clear that intermittent spikes in decibel levels—almost on par with a heavy metal concert—were inherently problematic. The problem was not limited to agitated amygdalae. The interference of the screeching trains probably broke students’ concentration, sending them off into their discursive thoughts, undermining their ability listen. External noise likely fed InternalThe noise from mental chatter is disruptive to attention and can lead to challenges in cognition and memory.

Although noise is becoming more obvious, it has a deeper and greater impact on the body and mind than interruptions or stress.

Imke Kirste (then a Duke University Medical School Professor) conducted an extraordinary study several years back to examine an ancient question. “Is silence really golden?”

Kirste and her team put mice inside anechoic chambers—tiny virtually soundless booths—for two hours a day. Then they tested the effects on their brains of five types of sounds: white noise, mice pup sounds, Mozart’s “Sonata for Two Pianos in D,” ambient noise, and silence. Following the application of each sonic variable, her team measured cell growth in each mouse’s hippocampus—the region of the brain most associated with memory.

Kriste and team thought that puppies would give the strongest results. But, the truth is that they discovered that mice responded best to silence. This resulted in the generation of the largest number of neurons that have been grown over time. “Functional imaging studies indicate that trying to hear in silence activates the auditory cortex,” they wrote.

It’s a simple but powerful notion: “trying to hear in silence” can demonstrably accelerate the growth of valuable brain cells. Listening to silence in its own right can enhance our ability to think clearly and to see.

This idea is not new. “Learn to be silent,” the ancient polymath Pythagoras advised his students. The Greek philosopher and forerunner of modern geometry told his inner circle of pupils to: “Let your quiet mind listen and absorb the silence.” The 15th Century humanist John Reuchlin explained that Pythagoras saw the practice of being in silence as “the first rudiment of contemplation”—the prerequisite to all wisdom.

There’s also the millennia-old Indian tradition of Nada Yoga, sometimes known as “the yoga of sound.” Some teachers describe the practice as tuning-in to the “sound of silence.” Distinct from other meditation practices—which generally focus on watching the thoughts or noticing the breath—the instruction in Nada Yoga is to just listen. Just pay attention to what is going on around you and the ringing within your own ears.

In Imke Kirste’s analysis, the power of listening to silence isn’t just pure relaxation. Contrary to what she thought, her coworkers discovered that deep listening in silence can be an effective way of achieving a sense of calm. positive stress, called “eustress.” Of the various stimuli they studied with the mice, they wrote, silence was “the most arousing, because it is highly atypical under wild conditions and must thus be perceived as alerting.” While the study authors agree that most everyday stress undermines the growth and healing of the brain, they see eustress as something different—the kind of exertion that makes us grow beyond our limitations.

So, if you’re able to take some time in silence, you don’t necessarily need a sophisticated meditation practice to harness its benefits for health and cognition. Just listen. Take some time and listen.

Silence is a virtue in an age filled with so much noise.

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