Hear the sounds of cicadas as trillions emerge in the U.S.

It's a big year for periodical cicadas.

Unlike their green-tinged cousins, the annual cicadas, periodical cicadas have a life cycle that spans more than a decade. They spend most of this time underground, before emerging every 13 or 17 years in massive generational groups scientists call "broods."

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Each brood is distinguished by its geographical location, and this year, two broods in the United States are set to emerge simultaneously for the first time since 1803.

Brood XIX emerges in the southeastern states every 13 years, while Brood XIII comes out in Illinois every 17 years. Between them, trillions of cicadas are emerging to fill the air with their high-pitched buzz from Maryland to Oklahoma, and Illinois to Alabama.

The bugs are so loud, people in South Carolina have resorted to calling the police over the noise.

Listen to them in the video above.

With files from The Associated Press

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  A periodical cicada sits on a tree leaf Tuesday, June 19, 2007, at a campsite in Scott County Park near Parkview, Iowa. (AP Photo/Quad-City Times, John Schultz).