Cicadas: When Are They the Loudest?

In Illinois, two broods of periodical cicadas are emerging: the 13-year cicadas in central and southern Illinois, and the 17-year cicadas in central and northern parts of the state. This means billions of cicadas will be creating their signature buzzing and clicking sounds.

The noise can be intense. During their last emergence three years ago, the high-pitched sound reached levels of 90 to 100 decibels. For comparison, this is as loud as a lawnmower, hairdryer, or motorcycle. However, according to the Centers for Disease Control and Prevention, this level of noise exposure is unlikely to cause hearing loss.

What Exactly Is That Sound?

The buzz is the mating call of male cicadas. 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 is 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 make a sound to attract males, but it’s a clicking noise produced by their wings.

When Are They the Loudest?

The loudest cicada activity typically occurs during warm, sunny, dry days with calm wind conditions. There’s a “just-right” Goldilocks zone of weather that maximizes their volume.

The emergence of billions of cicadas is underway, particularly in northern Illinois with Brood XIII, which was born in 2007. In central and southern Illinois, Brood XIX is making its appearance. The last time these two broods emerged together was in 1803, during Thomas Jefferson’s presidency.

For more information on how cicadas might affect your home, kids, pets, and garden, WGN has useful resources and advice.