Nature & Environment

Unraveling the Secrets of the Deafening Cicada Song: Insect Mating Call Revealed

Catherine Griffin
First Posted: Jun 05, 2013 10:39 AM EDT

The cicada invasion is finally occurring along the East Coast as the insects emerge from their 17-year slumber. As they do, they're making quite the racket with their deafening chorus of mating calls. Now, scientists have unraveled the secrets behind the song of the cicada, which may allow researchers to develop better sounding equipment.

Cicadas are some of the noisiest insects in the animal kingdom. The brood that's currently emerging along the East Coast, in fact, can produce sounds that can reach up to 100 decibels, according to LiveScience. While this ability has annoyed suburbanites over the years, it's fascinated scientists who hope to better understand the mechanism that allows them to make their calls.

In order to better study these cicada calls, the researchers used microcomputed tomography--a kind of CT scans that picks up details as small as a micron in size--in order to image a cicada's tymbal. Scientists have long known that the insect's tymbals on its exoskeleton are the source of its noise. The insect can rapidly vibrate these drum-like plates in order to produce its call.

Cicadas actually have two tymbals, one located on either side of its abdomen. The structure is made of a thin membrane connecting thicker sections known as ribs, each of which is thinner than a human hair. By scanning these structures, the researchers were able to gather a series of cross-sections and then assemble them via computer in order to get an extremely detailed picture of a tymbal, according to ScienceNow.

After examining the image, the researchers made some surprising findings. They discovered that the cicada makes noise by actually buckling the timbal. This means that the cicada is essentially compressing its body inward before springing it back into shape about 300 to 400 times per second. This particular buckling is unusual in the insect world; for example, crickets and katydids use a rubbing motion with their legs to produce sound.

That's not all the researchers found, though. It also turns out that the left and right tymbals act like two speakers that produce sound waves that constructively combine. This, in turn, allows the cicada to be far louder than they would be if the tymbals instead acted like a single speaker, according to ScienceNow.

The findings could have implications for creating devices inspired by the cicada's ability. These devices could be far smaller than traditional ones, and could send loud sounds long distances at lower power.

The findings were presented at the International Congress on Acoustics in Montreal on June 3.

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