How Do Cicadas Make Noise? (In Slow Motion) - Smarter Every Day 299

Episode Overview

• The episode revisits a scientific question that the host, Destin, failed to answer in Peru in 2012: how exactly a cicada makes its incredibly loud sound.
• Destin documents the massive scale of the 2024 dual-brood cicada emergence in Alabama, showcasing their overwhelming presence in everyday life.
• Using ultra-high-speed cameras filming at up to 110,000 frames per second, the team successfully captures the complex, multi-stage motion of the cicada's sound-producing organ, the tymbal.
• Through analysis with a sound designer and scientific papers, the episode breaks down how the tymbal's progressive buckling and subsequent vibrations create the cicada's two distinct frequencies.

Key Concepts

• Tymbal Mechanism: The primary sound-producing organ in a cicada, which consists of ribbed membranes that buckle and vibrate when pulled by muscles. This action is analogous to clicking the lid of a Snapple bottle.
• Resonance Chamber: The cicada's hollow abdomen acts as a resonance chamber, amplifying the sound produced by the tymbals, much like the body of a guitar amplifies the sound of its strings.
• Progressive Buckling: The slow-motion footage reveals that the tymbal's ribs don't buckle all at once but in a rapid, sequential wave. This progressive collapse is what produces the lower-frequency component of the cicada's call.
• Dual Frequency Sound: The cicada produces two main sounds simultaneously. The lower frequency drone comes from the progressive buckling of the tymbal's ribs, while a higher frequency buzzing sound is generated by the rapid vibration or "wobbling" of the pleats after they buckle.
• Constructive Interference: Because cicadas have two tymbals on opposite sides of their hollow abdomen, the sound waves they produce can combine and amplify each other, making the overall sound significantly louder.

Quotes

• At 00:43 - "It's kind of like the top of a Snapple bottle... However, what's really cool about these guys is this bottom part of its body is actually hollow, and that serves as a resonance chamber." - Entomologist Phil Torres provides an analogy to explain the basic mechanics of how a cicada produces its sound.
• At 10:30 - "Oh! Whoa! Oh!" - This is host Destin's raw, excited reaction upon seeing the first successful ultra-slow-motion footage of the cicada's tymbal vibrating, finally capturing the phenomenon he had sought for years.
• At 17:23 - "It's like a progressive buckling." - After observing the slow-motion footage and reading a scientific paper, Destin articulates the key mechanical insight: the tymbal's ribs collapse sequentially rather than all at once.

Takeaways

• A cicada's loud call is a sophisticated two-part system: a vibrating "tymbal" organ creates the initial sound, which is then massively amplified by its hollow abdomen acting as a resonance chamber.
• The unique sound of a cicada is not a single click but a complex combination of two frequencies created by a single mechanical action: a low-frequency sound from the progressive buckling of the tymbal's ribs, and a high-frequency sound from the subsequent vibrations.
• The sheer scale of periodic cicada emergences is a remarkable natural event, showcasing the incredible numbers and impact these insects can have on an ecosystem and local human life.
• Persistence in scientific inquiry pays off; what was unachievable with the technology of 2012 became possible with more advanced high-speed cameras, allowing for a deeper understanding of a common natural phenomenon.