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Saving Silence

This article was written by Sarah Rich in January 2007. We're republishing it here as part of our month-long editorial retrospective.

For several years, I lived in an apartment in San Francisco where my bedroom window faced directly onto Haight Street. The quietest time of day fell somewhere between the bar-hoppers and homeless retiring to their respective sleeping quarters, and the early cooing of pigeons and idling of delivery trucks. But that's not to say it was ever truly quiet. Like most city-dwellers, the sounds of the street became more peaceful than silence, in a way, and I didn't really mind the near-continuous melodies of horns, sirens and voices. Sound, like smell, is something we adapt to much more quickly than physical changes in our surroundings. But the behavioral changes we make according to our soundscape can in fact be a powerful indicator of environmental and cultural trends in our region.

Even more powerful are the adaptations we can observe in wildlife as their habitat changes due to the presence of human activity. This is the primary focus of the Acoustic Ecology Institute, a New Mexico-based non-profit working to "increase personal and social awareness of our sound environment, through education programs in schools, regional events, and our internationally recognized website," and to build "a comprehensive [online] clearinghouse for information on sound-related environmental issues and scientific research."

Perhaps the best way to understand their work is to hear about a few examples offered up in their recent news posts:

Study Confirms Birds' Changing Songs in Cities - Field studies in ten European cities, including London, Paris, and Prague, have confirmed that great tits adapt their songs to be better heard above a variety of noise conditions. The city-dwelling birds, a species that has adapted well to urban settings, were compared to forest-dwelling birds nearby. In songs important for mate attractions and territory defense, the urban songs were shorter and sung faster than the forest songs. The urban songs also showed an upshift in frequency that is consistent with the need to compete with low-frequency environmental noise, such as traffic noise. The capacity of great tits to sing within a relatively wide frequency range, and the ability to adjust songs by leaving out lower frequencies, seems critical to the bird's ability to thrive despite urban noise. Species without these capacities may have no other choice than to escape city life. An earlier study by the same researchers had identified frequency differences in great tit songs in one urban area, reflecting the amoung of low-frequency noise they had to be heard above; this study expands the findings to include many populations of tits, and compares urban to rural populations.

Another story that struck me for its artistic quality is the installation of "One Square Inch of Silence" in Olympic National Park by natural sound recordist and master listener, Gordon Hempton. His project stood as a call to the National Park system to establish sonic refuges within park boundaries, where increased visitor traffic has tainted the purity of the soundscape and generally raised the volume throughout the otherwise protected acreage. "Quiet is going extinct," he says. His installation can be found by following directions on his website. Visitors are invited to scrawl their impressions quietly on a piece of paper and leave them in a jar at the site.

It's not just about nature and wildlife, though. The AEI tracks advances in science and medicine through sound, such as a study published by the Optical Society of America illuminating the possibility of early detection of metastasizing melanoma by listening to sounds emitted by cancer cells:

The unprecedented, minimally invasive technique causes melanoma cells to emit noise, and could let oncologists spot early signs of metastases -- as few as 10 cancer cells in a blood sample -- before they even settle in other organs...The team's method, called photoacoustic detection, combines laser techniques from optics and ultrasound techniques from acoustics, using a laser to make cells vibrate and then picking up the characteristic sound of melanoma cells. The microscopic granules of melanin contained in the cancer cells absorb the energy bursts from the blue-laser light, going through rapid cycles of expanding as they heat up and shrinking as they cool down. These sudden changes generate ultrasonic sounds which propagate in the solution like tiny tsunamis.

Their areas of inquiry span ocean, wilderness and metropolis, revealing a huge amount of information about our changing planet just by taking the time to listen.


Acoustic Ecology and the Extinction of Silence is part of our month long retrospective leading up to our anniversary on October 1. For the next four weeks, we'll celebrate five years of solutions-based, forward-thinking and innovative journalism by publishing the best of the Worldchanging archives.

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