Feature Sound: Snapping Shrimp


Courtesy of the Department of Applied Physics, University of Twente

They sound like a string of firecrackers going off, or a sheet of bubble wrap rapidly being popped. Pound for pound, the worst noisemakers in the sea, their din is so pervasive that submarines have successfully used this racket as cover to confuse enemy sonar.

For decades scientists believed the mysterious ‘snapping shrimp’ made those unusual sounds by rapidly snapping together the two pincers of their one oversized claw. The popular view was that the shrimp were creating this racket by the equivalent of finger-snapping, ala aquatic beatniks. Apparently Charlie the Tuna was not the only sea creature to wear a beret. Then in September of 2000 a team of scientists photographed the shrimp at 40,000 frames per second, only to discover the sounds came from collapsing air bubbles.

This process is called cavitation. It is the formation of gas-filled bubbles in liquids in motion when the pressure is reduced to a value less than the vapor pressure of water when the surrounding temperature remains constant. Cavitation occurs when the shrimp slam shut their oversized claws at extremely high speeds.

Snapping shrimp use this quirky method to stun prey. Not wild enough for you? A year after the first discovery, scientists found that snapping shrimp not only, snap and crackle, they pop, too. The gases in the collapsing bubbles, which can heat up to 20,000 degrees C, cause a ‘flash’ of light termed ‘sonoluminescence.’ So far, they’re the only living creatures that can claim this distinction. It’s a wonder Disney hasn’t optioned them.

-Nancy Craven

Snapping and popping sounds produced by the same shrimp recorded above, however the playback speed is reduced to half to demonstrate the high frequency of the snaps and pops. Courtesy of Paul Perkins, NUWC Engineering, Test and Evaluation Department.