ONE OF THE FIRST THINGS OUR KIDS LEARNED...:

"Listen," said Bernie Krause. He rolled down his car window, and we sat silently for a moment. It was an hour before dawn, still dark and foggy in the Mayacamas Mountains, a northern California coastal range. But somewhere in the distance, a bird was calling--a high, bright, lively song that seemed at odds with the misty gloom. "A song sparrow," Krause whispered. "They're always the first to sing here." The sparrow's opening notes meant that this day's dawn chorus had begun. Wherever wild birds live, mornings start this way, with males ascending to their perches to sing and welcome the day. "The dawn chorus is one of the earth's best and oldest songs," Krause said, grabbing his recording equipment and tripod. "But most of us in the industrialized world have never heard it. And it's disappearing."

Despite years of camping, I'd never listened so intently to the birds' celebration of sunup, so I hurried along with Krause down a gravel trail, eager to hear more. Other bird species would soon be adding their voices to those of the sparrows, and Krause wanted to capture the full choral effort on his digital recorder. The 73-year-old Krause is a bioacoustician (he prefers the term soundscape ecologist), though in another life he was one of the first masters of the Moog synthesizer. He had worked with The Doors, Mick Jagger, and Van Morrison, but gave up the glamour of rock and roll in the 1970s to travel the world and record its vanishing biophony--a term he coined to describe the planet's natural, non-human sounds. Many of those journeys took him to exotic locales--Rwanda for gorillas, the Amazon for jaguars, Alaska's Glacier Bay for humpback and killer whales. Yet every month for 17 years he has come to this same spot in the Mayacamas, not far from his Sonoma County home, to record the birds at dawn. It is one of the best places left in California, he'd told me earlier, to hear the dawn chorus uninterrupted by cars, jets, leaf blowers, generators, or any of the multitude of motorized noises that make up our modern cacophony.

"Usually, it's an hour or so before we hear the first motorcycle or airplane," he said, stopping at his chosen spot to attach his microphone to the tripod. He set it among some low-growing bushes, pointed it toward the oaks and chaparral that bordered a stream, plugged the headphones into the recorder, and handed them to me. "This is what changed my life," he said. "Stand quietly, try not to move."

I put on the headphones and was suddenly engulfed in birdsong--so much so that for a moment I took them off to look around. Where were all these birds? The sun's first rays were just lighting the foggy gray around us, and I thought I should be able to see them. Certainly, I could hear them through the headphones. Krause smiled, understanding my bewilderment. "Just listen," he advised. I put them back on, and once again felt the slight disorientation of being pulled into an invisible world, one I had never known existed. Goldfinches added their quick, metallic notes to the more melodious calls of the sparrows; robins and grosbeaks whistled sweetly, juncos chirped, and towhees wheezed tow-wheee, tow-wheee. Every few minutes, another species joined the chorus, creating the morning's biological symphony. I was instantly addicted, and I wanted to know why. Even more, I wanted to know why these once ubiquitous choruses are in such decline. And not just birdsong but many of the natural noises that Krause and other bioacousticians say are highly imperiled, such as those of frogs and fish. That meant asking Krause some questions, so I reluctantly gave up the headphones. We left the microphone in place and the recorder running while we took a walk.

"What you're hearing through the headphones is the world the way our ancestors heard it, before mechanical sounds dominated everything," Krause explained. "The microphone pulls in the biophony, so it seems that you're in your own private music hall. You can get lost in this," he added with a smile. The sounds are also captivating because they follow a pattern similar to a musical score, he contends, and because they restore our sense of balance with nature. "We rarely listen--really listen," he said, recalling a night hunt he once joined with the Jivaro people in the Amazon Basin. They used the cries and trills of frogs and insects to find their way and to locate their prey, while Krause stumbled along anxiously after them in the dark. "They were at ease in the forest because they could interpret what they heard, but most of us have lost that ability."

That's partly because we now live in such a visually dominated world, where image is everything--think TV, film, the Internet. And even when we put in the earbuds of our iPods, we often do so to block out the contemporary clamor and retreat to our own private aural universe. "I'm not against people," Krause said. "I'm pro people. But we'd all be healthier if we had stronger connections to these natural soundscapes."

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