"There are no words that can tell the hidden spirit of the wilderness, that can reveal its mystery, its melancholy, and its charm." —Theodore Roosevelt, 1910

"The day will come when man will have to fight noise as inexorably as cholera and the plague." —Nobel Prize–winning bacteriologist Robert Koch, 1905

Silence is something you assume you will always be able to find if you need it. All you have to do is drive far enough in the right direction, trek through quiet fields or woods, or dive into the sea's belly. For true silence is not noiselessness. As audio ecologist Gordon Hempton defines it, silence is "the complete absence of all audible mechanical vibrations, leaving only the sounds of nature at her most natural. Silence is the presence of everything, undisturbed."

And silence, Hempton believes, is rapidly disappearing, even in the most remote places. He says there are fewer than a dozen places of silence—areas "where natural silence reigns over many square miles"—remaining in America, and none in Europe. In his book, One Square Inch of Silence: One Man's Search for Natural Silence in a Noisy World, written with John Grossman, Hempton argues that silence—a precious, underrated commodity—is facing extinction. Over the past three decades Hempton has circled the earth three times, recording sound on every continent except Antarctica: butterfly wings fluttering, coyotes singing, snow melting, waterfalls crashing, traffic clanging, birds singing. His work has been used in film soundtracks, videogames, and museums.

He has also trekked through both remote and urban landscapes, measuring decibels and rude interruptions to the noises of nature. In 1983 he found 21 places in Washington state with noise-free intervals of 15 minutes or more. By 2007 there were three. (One of them is Olympic National Park, which he is trying to save, and he will not reveal the names of the others, arguing that they are protected by their anonymity.) Whom can we blame? People, and planes. Hempton claims that, during daytime, the average noise-free interval in wilderness areas has shrunk to less than five minutes. Think of the snowmobiles roaring through Yellowstone, helicopters flying over Hawaii volcanoes, and air tours over the Grand Canyon. It is air trafficthat Hempton seems to resent the most: in his book, he travels across the United States in a 1964 VW bus, recording sound as he goes, from Washington state to Washington, D.C., where he meets with politicians and officials to press his case for the preservation of natural silence.

I spoke to Hempton about his work, his mission, and whether he is just a cranky leaf-blower-hating hippie.

Why should we care about silence? 
It has become an increasingly rare experience to be in nature as our distant ancestors were. Even in our national parks today, despite laws to protect them, you are much more likely to be hearing noise pollution, particularly overhead aircraft, than you are to be hearing only the native sounds of the land. Yet to be in a naturally silent place is as essential today as it was to our distant ancestors. Besides spending time away from the damaging noise impacts present at our workplace, neighborhoods, and homes, we are given the opportunity not only to heal but discover something incredible—the presence of life, interwoven! Do you know what it sounds like to listen for 20 miles in every direction? That is more than 1,000 square miles. When I listen to a naturally silent place and hear nature at its most natural, it is no longer merely sound; it is music. And like all music, good or bad, it affects us deeply.

Have you always been interested in silence? Were you a child with acutely sensitive hearing? 
As a young child, I was very close to the natural environment. For my first four years, we lived in Hawaii and all my friends could fit in my pockets—they were bugs. My brother, sister, and I ran wild. We moved back to the mainland eventually, but I clearly remember sliding to the bottom of a swimming pool and loving it. It was such an unusual silence, it was like I was suspended in time as I was holding my breath.

At college I majored in botany, and I was outdoors in vegetation all the time. But I did not really start thinking of silence until I was a graduate student in plant pathology, when I was driving from Seattle to Madison, Wis., and decided to sleep in a cornfield for the night. I didn't want to pay for a hotel. As I lay there I heard crickets, and rolling thunder in the background, which captivated me. The thunderstorm came, and I truly listened. The storm passed on, and as I lay there, drenched, the only thought in my mind was, how could I be 27 years old and never have truly listened before? I then took my microphone and tape recorder and went everywhere, obsessively listening—freight trains, hobos—it was a flood of sensation. I realized how we need to hear to survive—in evolution, earlids never developed, but eyelids did. And to those who know that true listening is worship, silence is one of nature's most transformative sermons. I am filled with gratitude to have heard it. Max Ehrmann was right-on when he wrote: "Go placidly amid the noise and haste, and remember what peace there may be in silence."

Could too much silence make you mad? 
Yes, too much silence will drive you mad in no time at all if you are talking about spending time alone in an anechoic chamber. That fact is well established. But in nature, experiencing too much natural silence will not drive you mad—in fact, it might make you sane. Recent studies have shown that nature experience can be as effective as medication in the treatment of autism, for example.

What can we do to save natural silence? 
First, go and experience it. Second, contact members of Congress and tell them to support your right to quiet—specifically, that the FAA needs to route aircraft around our most pristine national parks unless it is a rescue operation or other reasons to preserve life. The Organic Act of 1916 created the National Park Service to manage our national parks to remain "unimpaired" for present and future generations. Yet while natural quiet is listed as a protected natural resource, 90,000 air tours flew over Grand Canyon National Park in 2009, and another 90,000 air tours will fly again in 2010!

What has been the response to this campaign to reroute aircraft, which you outline in your book? 
Airline response has been good but limited. Alaska, American, and Hawaiian Airlines have all volunteered not to fly over Olympic National Park for some flights but not all. The catch is that the FAA has placed four jetways directly over Olympic park: three that crisscross the heart of the park and one that follows the Olympic National Seashore. These jetways are like interstates in the sky, but unlike the interstates that we drive on, there is no pavement to remove or expensive relocation construction cost. These jetways should be moved to protect Olympic park. This area is currently the least polluted by noise when compared to any of the other approximately 390 units managed by the National Park Service. Even more significantly, Olympic park has the greatest diversity of natural soundscapes: glacier-capped peaks, the best example of temperate rainforests in the Western Hemisphere, and the longest uninterrupted stretch of wilderness seashore in the Lower 48.

How do we find silence? 
The way to find silence is to go to onesquareinch.org and get directions. The way to begin to find the other 11 places in the U.S. is to look at a NASA view of the United States at night. Light pollution is the evil cousin of noise pollution. Then find a black space that is not between major cities (hint: look to the faraway corners of this country and the northern boundary with Canada).