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Cicada Calls Are Literally Deafening

They're coming.
May 3, 2016, 6:04pm
Image: Flickr/Eric Stavale

Gird your loins, cover your ears, and prepare to surrender your lawn to billions of teenage arthropods. The cicadas are coming.

In a couple of weeks, Brood V will begin its ascent from under the Earth to burst forth in a cacophony of rebirth, hunger, and sex. Residents of several East Coast states will be able to witness (and hear) the fruition of the brood's 17-year life cycle, which won't appear again until 2033.

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Anyone who's ever experienced a cicada season knows that "loud" is an understatement when it comes to describing the sounds they emit. I was around Washington, DC, for their 2013 emergence, and the only thing worse than inevitably stepping on them was trying to find some peace and quiet. But, as I learned, cicada calls aren't just clamorous—they can actually be deafening.

Cicadas are wondrous, little insects, and their developmental synchronization is one of nature's many mysteries. Biologists still aren't sure why or how cicadas emerge in such a punctual and plague-like manner, but they do know to expect a swarm every 17 or 13 years.

Once a brood breaches the soil in which it's been hibernating, the cicadas find a safe place to molt into their final form. After their exoskeletons have hardened, males will begin to perform their mating call: a raucous, grating rattle that I like to compare to the revving of a very tiny, very annoying motorbike engine.

Scientists who study hearing and human ear health have warned that cicada calls are loud enough to cause "physical and psychological strain in humans." Entymologist John Petti estimated that Tibicen walkeri, an North American cicada, can emit sounds hitting 108.9 decibels. According to a loudness scale, that's noisier than a jet during takeoff, a power lawn mover, and a jackhammer.

Billy Martin, a hearing scientist who leads Dangerous Decibels, a public health campaign designed to reduce noise-induced hearing loss, is concerned about cicadas' effect on poor, human bystanders.

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"Loud sound is very stressful, especially if the sound is annoying and loud," Martin told Phys.org. "It's the double whammy and cicadas, for the most part, are both."

A study conducted by a group of entomologists in 1995 measured the mating songs of 30 species and the alarm calls of 59 species—all North American cicadas—and discovered that mean sound pressure levels ranged from 79.8 to 106.2 decibels.

Here's some more perspective: The US Occupational Safety and Health Administration ruled that 8 hours of exposure to noises reaching 90 decibels, or two hours of exposure to 100 decibels, are the maximum permissible levels for noise safety.

A cicada is capable of causing such a racket due to vibrations of its "tymbals," or sound production organ composed of corrugated exoskeleton. The insect will actually deform its body to contract at rates of 300 to 400 times per second. In humans, this would be tantamount to sucking in your ribcage to the point of collapse, and then releasing it again. And because a cicada's abdomen is uniquely hollow, the sounds that emerge from it are amplified to much higher levels.

Currently, Dr. Derke Hughes, a researcher at the Naval Undersea Warfare Center, is working on a project that aims to create a physics-based model for cicada sound-making. Up until now, scientists have never been able to replicate the cicada's call in a lab. But Dr. Hughes hopes his efforts will open the door for better sound propagation technology, such as lighter, more efficient sonar devices.

So in a dozen or so days, when the first nymphs begin to peek their tiny, translucent heads out of your lawn, stick your fingers in your ears, and run away screaming "NIMBY!" Just kidding. Unless you're spending a ton of time outdoors, you probably have nothing to worry about. Instead, you could just go inside, shut your windows, and marvel at the sounds of a billion creatures trying to get it on.