La #soundscape_ecology, ou étudier un écosystème par le son.
Eavesdropping on Ecosystems
Sueur and his colleagues weren’t interested in exactly which species were calling. Instead, he says they wanted “to take a global measure of the acoustic output of the community.” Their goal was an algorithm that could boil hours of acoustic data down to a single number describing how an ecosystem’s acoustic energy is distributed across the frequency spectrum and over time.
The boom in sound-recording studies poses a challenge familiar in other fields: a glut of data. Pijanowsky’s lab alone has amassed about 85 terabytes of sound—more than 100,000 hours—in just 5 years. “This is a science that’s plagued by the big data challenges that you see in, say, genetics,” he says. Many researchers already have libraries of field recordings that, if played in real time, would be longer than their careers. “We know that we’re not going to be able to listen to it all,” says computer scientist Michael Towsey of the Queensland University of Technology in Brisbane, Australia.
To get around that problem, he’s developing ways to navigate soundscapes by sight, creating color-coded spectrograms that trained eyes can interpret at a glance. Towsey describes the visualizations as “#acoustic_weather” charts. Some show how the spectrum of sounds shifts over a single day, while others assemble daily records into long-term snapshots to capture changes between seasons or years. That’s akin to studying the “#acoustic_climate,” he notes. And “when we start thinking about the acoustic climate, then we can start thinking about acoustic climate change.” Year-to-year comparisons could eventually highlight subtle and potentially problematic changes, he predicts, such as changing rain patterns or shifts in bird activity.
Computer scientist Michael Towsey combines 8 months of continuous recordings at a research station in Brisbane, Australia, into a single image. Colors indicate different acoustic indices. At dawn (left curve), a morning bird chorus (blue) is obvious during the Australian spring and early summer (October through December), but fades later in the year. Horizontal green streaks indicate heavy rainfall in January and February. At dusk (right curve), cicada activity is evident in the spring and summer months (green); by winter, the night is increasingly silent.