Is Silence Going Extinct? - NYTimes.com Peter van Agtmael/Magnum, for The New York Times Davyd Betchkal, sound catcher, in Denali National Park and Preserve in Alaska. Setting off in the predawn gloaming of central Alaska, we were the sounds of swishing snow pants, crunching boots and cold puffs of breath. As sunrise gradually lightened the late November sky, we took visible shape: a single-file parade on a narrow white trail traveling west, deeper into Denali National Park and Preserve. It was three degrees and so still that when we pulled up to rest, I heard no wind, no sibilant leaves, just a barely perceptible ringing in my ears. Tundra swans, kestrels and warblers had all flown south. Grizzlies were asleep in their dens. We tramped over frozen streams and paused to discover water still trickling faintly in hollows below. To the north, a morning blast of pink and orange brightened snow-shrouded Mount Healy at the edge of the Alaska Range; to the south - where the sun is always rising or setting during winter at a latitude just three degrees shy of the Arctic Circle - an alpine ridge remained covered in shadow and alder. We saw a beaver hut on a frozen pond and moose tracks in snow. Ice frosted the nettles of black spruce and the beard of our leader, Davyd Betchkal, the park's physical-science technician. Betchkal's beard recalled that of his hero, the naturalist Henry David Thoreau, at the start of the Civil War. Otherwise he was a 25-year-old Wisconsinite wearing a lime green hat knit by his mother. He and I shouldered backpacks each weighted with 30 pounds of recording equipment. Far up ahead, a park ranger on skis towed more gear by sled. Our destination was a ridge above Hines Creek, where Betchkal planned to assemble a station to collect a month's worth of continuous acoustic data documenting an intangible, invisible and - increasingly - endangered resource: natural sound. Our mission was not only to trap the ephemeral but also to experience it ourselves, which at the moment was impossible for three reasons: 1) the chafing of our nylon outfits; 2) the chunking of our military-issue Bunny Boots on ice; and 3) planes. "If you're on foot and you choose to focus on the natural quality of the landscape, you're completely immersed in nature; nothing else exists," Betchkal said to the back of my head, letting me set the pace as we traipsed steadily uphill. Then a jet will go over, and it kind of breaks that flow of consciousness, that ecstatic moment. Meditating on our surroundings, I became a little curious how much farther we had to go. "Don't think about that - that's my answer," Betchkal called ahead cheerfully. Another answer is that I don't know. An undeveloped swath of land nearly the size of Vermont, Denali should be a haven for natural sound. Enormous stretches of wild country abut the park in every direction save east, where Route 3 connects Fairbanks to Anchorage. One dead end and mostly unpaved road penetrates the park itself. Yet since 2006, when scientists at Denali began a decade-long effort to collect a month's worth of acoustic data from more than 60 sites across the park - including a 14,000-foot-high spot on Mount McKinley - Betchkal and his colleagues have recorded only 36 complete days in which the sounds of an internal combustion engine of some sort were absent. Planes are the most common source. Once, in the course of 24 hours, a single recording station captured the buzzing of 78 low-altitude props - the kind used for sightseeing tours; other areas have logged daily averages as high as one sky- or street-traffic sound every 17 minutes. The loudest stretch of the year is summer, when hundreds of thousands of tourists flock to Denali, embarking on helicopter or fixed-wing rides. Snowmobiles are popular with locals, and noise from the highway, the park road and daily passenger trains can travel for miles. That sort of human din, studies are beginning to suggest, is imperiling habitat - in Denali as well as wilderness areas around the world - as surely as a bulldozer or oil spill. But scientists have so little information about what landscapes should sound like without human interference that trying to correct the problem would be like a surgeon's wielding a scalpel without knowing the parts of the body, let alone his patient's symptoms. To restore ecosystems to acoustic health, researchers must determine, to the last raindrop, what compositions nature would play without us.