Our planet fizzes and crackles with a rich cacophony of sounds—but it constantly changes over time. Now, a team of scientists want to record the noises that surround us each and every Earth Day—which just happens to be today—to see exactly how it alters over time.

Led by Bryan Pijanowski, the idea is to enlist thousands of people across the world to use the Soundscape Recorder smartphone app to save the sounds that fill our ears for future research. Over time, he hopes to analyze the recordings to measure how our sonic environment is changing.

While Pijanowski usually works in remote locations—like the Sonoran desert or rain forests in Borneo—he's particularly interested in the noises within cities, towns and suburbs. The idea is simple: you download the app, record the sounds of your surroundings, then answer a few questions about where you are, what you heard and how you feel. The data's then uploaded to the Global Soundscape database for analysis.

By pinning the recording initiative to Earth Day—which happens every year on April 22nd—Pijanowski hopes to make it "something everyone goes out and does" so that he "can begin to characterize those sounds and compare them from year to year." Over time, he'll work out whether our planet is getting noisier, how the sounds we make are changing, and what it means for the world to inhabit. Go download the app and get recording. [Soundscape Recorder via Wired]