Beautiful sounds like the rhapsodic strings in an orchestra or the melody of a song bird can be stunning. Not surprisingly, several comic characters take this metaphor and make it reality (as real as comics can be, that is). The crime fighter Black Canary can produce a cry from her super vocal chords that can break things, knock people out and, as an absolute last resort, put the kibosh on them completely. Fellow good guy and physician Dr. Mid-Nite has determined that Black Canary’s cry reaches into the ultrasonic range. This, according to him, is what spells lights out for the bad guys. From this diagnosis we can derive only one, inescapable conclusion: Dr. Mid-Nite is a quack.
Black Canary (c) DC Comics
Humans can’t hear ultrasound and as a consequence shouldn’t be affected by it. Imagine how awful it would be if we were. Every summer barbeque would have to wrap up at dusk so that the intense ultrasonic cries of echolocating bats didn’t make us pass-out on our sizzling grills and impale ourselves on our croquet wickets. No, it is clear that the good doctor got it wrong. Fortunately, scientists in this dimension have identified a few critters that can incapacitate (and kill) with sound. Enter the snapping shrimp.
Snapping shrimp. Note the big right claw. Figure from Versluis, et al. (2000) Science 289, 2114
The snapping shrimp is about the size of half a hot dog and it has one claw that is much bigger than the other (see image above). When the snapping shrimp leaps into battle it puts the hurt on its foes by snapping it’s big claw ridiculously fast. As the claw closes during a snap, it shoots out a jet of water. No big deal, right? Every kid at the pool can do that. But this jet of water moves faster than the surrounding water can rush in to replace it and a bubble of air stretches out in its wake. But the gas in this bubble (called a cavitation bubble) is extremely thin and it rapidly collapses under the pressure of the surrounding water. When this happens, the collapsing water produces a high-pressure sonic pulse that can stun or even kill a small fish within 4 cm.
Time lapse of cavitation bubble formation and change in sound pressure. Figure from Versluis, et al. (2000) Science 289, 2114
During time lapse footage of the snapping shrimp closing its claw you can see the formation of the cavitation bubble (a couple of frames after the frame labeled 2 in the figure above) and it’s collapse (the frame labeled 3). The graph on the left shows the peak in sound pressure that corresponds with the collapse at 3. In other words: Ka-Pow! The sound created by the snapping shrimp is audible and a reef with a lot of snapping shrimp can sound like the shootout at the O.K. Corral. This might explain the snapping shrimp’s other moniker: the pistol shrimp. Hmmm. One animal, two names. Kinda sounds like a secret identity. I can see the comic book tag line now:
The Stunning Pistol Shrimp, Stopping Crime is Snap!
Versluis, M, Schmitz, B, von der Heydt, A and Lohse, D (2000) How Snapping Shrimp Snap: Through Cavitating Bubbles. Science 289, 2114