Cicada squeals and sound

Khao Sok National Park, Thailand

We first explored this rainforest jungle at dusk. We observed monkeys in the trees, a stick bug crossing the trail and immense crisscrossing bundles of bamboo above and around us. But the most memorable and intense part of our evening hike was the screeching hum of cicadas. As we walked down the trail, the shrill insect calls would shift – sometimes bearable, the next moment so harsh we had to cover our ears. We compared the cicadas’ vibrating wing songs to familiar sounds: a table saw, car alarm, metal on a chalkboard, an airhorn, the squeal of deflating a latex balloon, the propeller of a RC model airplane. When we recorded short clips and played them back, we could detect the differences in pitches.

Male cicadas vibrate their wings up to 400 times per second to produce their mating sound.

Our hike inspired speculation about the mating songs of these crazy loud insects and discussion about properties of sound waves:

  1. Why do you think the cicadas pitches vary? (Hint: there are around 2,500 different species in the park.)
  2. What unit do we use to measure sound volume? How loud do you think these insects are and what does their volume compare to?
  3. What is the relationship between frequency and wavelength of a sound wave?

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