Cicadas: When are they the loudest?

CHICAGO — They’ve begun to emerge . And they’re going to make their presence very much known.

In Illinois, two broods of periodical cicadas are coming out. In central and southern Illinois, its the 13-year cicadas. In central and northern parts of the state, it’s the 17-year cicadas. Together, it means billions of them will be making that signature buzzing and clicking.

And it can be loud. When they emerged three years ago, readings put the high-pitched sound in the 90 to 100 decibels range. By comparison , that can be as loud as a lawnmower, hairdryer or motorcycle. Still, your exposure to them is unlikely to cause hearing loss, according to the Center for Disease Control and Prevention .

What exactly IS that sound?

In short, the buzz is the male cicadas looking to find a mate. Arizona State University explains it this way:

“Both sides of their thoraxes have thin, ridged areas of their exoskeletons called tymbals. Tymbals are made of a rubbery substance called resilin. The cicadas vibrate their tymbals very fast using muscles in their bodies. With every vibration, a sound wave is released, and cicadas can send out 300-400 sound waves per second! … The abdomen of male cicadas are almost completely hollow. When sound waves from the tymbals enter this hollow area, they bounce around. This can change the sound, make the sound louder, or both.”

Females also emit a sound to attract males, but it’s a clicking sound from their wings.

When are they the loudest?

It depends on the weather conditions. There’s a just-right Goldilocks zone when you can expect them to be at their loudest.

Generally speaking, you’ll hear them the loudest on warm, sunny, dry days with a calm wind.

MORE CICADA COVERAGE:

• Beware: Cicadas could pee on you
• How to keep cicadas out of your home
• Cicada Trivia: Interesting, bizarre facts about the ear-splitting insects

For the latest news, weather, sports, and streaming video, head to WGN-TV.