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Courtesy of Michael Towsey

Interactive Gallery: Seeing Sound

It may seem like abstract art, but this image encapsulates 8 months of sound from the Australian countryside. Such feats of scientific synesthesia are a trademark of the emerging field of soundscape ecology. Thanks to networks of tough, automated recorders and powerful sound-analysis software, scientists are looking for patterns of sound to describe ecosystems and track how they change over time. To create the image above, computer scientist Michael Towsey of the Queensland University of Technology in Brisbane, Australia, assigned colors to three acoustic indices—numbers representing characteristics of a recording, such as the timing and frequencies of sounds present. The result reveals morning bird choruses (blue) throughout the Australian spring and early summer (October through December). Horizontal green streaks indicate heavy rainfall in January and February. Cidada activity (green) around dusk (right curve) fades as winter approaches. Such acoustic overviews are built by vertically stacking 24-hour recordings, which Towsey can also visualize in sharper detail:

Scientists hope to use images like these to assign a unique acoustic signature to an ecosystem. Changes in that signature can indicate how an environmental threat—such as the gradual effects of climate change or increasing levels of human noise pollution—disrupt animal communities. Sometimes, such degradation is obvious in the soundscape:

For more on the emerging field of soundscape ecology, see “Eavesdropping on Ecosystems” in this week’s issue of Science, and listen to the Science podcast interview.