Phenomena researches sonic enigmas and collaborates with experts in pursuit of an overlapping art + science.

The buzz of cicadas is a prominent sound associated with warmer seasons in many regions, evidenced by this anime trope. The sound we hear is a mating call, performed by male cicadas, to attract potential mating partners. And while there are over 3,000 species of cicadas, within their several-week lifespan aboveground, they’re all trying to do the same thing: ;). Every year we are greeted with various sounds from ‘annual cicadas, however, there’s also a group called ‘periodical cicadas’ which emerge from their resting places in the ground at very specific times.

National Geographic states “Of the 3,000 species of cicadas around the world, only seven species share synchronized life cycles that allow them to come out simultaneously every 13 or 17 years. These periodical cicadas, as they’re known, are only found in the central and eastern U.S.” With this new group, coined Brood X, emerging alongside annual cicadas this summer, we can expect hundreds of billions of cicadas. Knowing that this inescapable chorus of horny buzzing will be upon us soon, let’s investigate how the cicadas make their sound.

Under the cicadas’ wings, there’s an exoskeletal membrane called a ‘Tymbal’, this is the sound generator for cicadas. It’s somewhat like the human diaphragm: it contracts and expands to push air, creating a vibration, but according to Derke Hughes, a researcher at the Naval Undersea Warfare Center, “If your body were like that of a cicada, you would have a thick set of muscles on either side of your torso that would allow you to cave in your chest so far that all your ribs would buckle inward one at a time into a deformed position...The cicada repeats this cycle for its left and right sides about 300 to 400 times a second.” So the tymbal is less like the diaphragm and more like a hyperspeed accordion.

If you have any experience catching, accidentally stepping on or even intentionally eating cicadas, you’re aware that they have fairly hollow bodies too. This hollowness allows for the vibrating sound of the tymbal to resonate and be amplified just like the hollow body of an acoustic guitar amplifying the sound of struck strings. This relationship of air resonating from the tymbal into the hollow cicada body makes the cicada's “instrument” somewhat like a Helmhotz Resonator, a phenomenon of physics that can be recreated when you blow on the top of an empty bottle. There is a second part that makes up this resonator too: the Tympana, which are the sound receivers for cicadas; their ears basically, located on the underside of the abdomen. A 1995 study by Australian zoologists D. Young & Henry C. Bennet-Clark shows that “the sound at the outside of the tymbals is relatively quiet compared with that outside the tympana” (Young, 1990)

This led them to the conclusion that the process of sound production in cicadas is as follows: “muscle power > tymbal clicks > excitation of abdominal resonator > radiation of sound via tympana.” (Young, 1995) Every species of cicada may have a different song based on the speed and rhythm of this expansion and contraction of the tymbal too. The D. Young study, for example, examined the Cyclochila species of cicada and found “the sound energy is confined to a comparatively narrow bandwidth around 4kHz” (Young, 1995). Music professor David Rothenburg noticed the different timbres of the cicadas and has been playing music alongside cicadas as they emerge. On a recent episode of WNYC’s Radiolab he jams with this natural “orchestra” and when asked about Brood X, he plans to “get together the best musicians I can find to go out and play with them”. Now that we understand how cicadas make sound, we too can join in on singing songs of want and festivity written by beings emerging after a long moment of dark dormancy, not unlike our own collective emergence after this past year.