The acoustics of snapping shrimps

With an increased interest in acoustic daylight, the contribution of snapping shrimp noise has drawn considerable attention. These crustaceans are among the major contributors of biological noise in shallow waters of temperate and tropical regions. The shrimp produce sounds by rapidly closing one of their frontal claws, snapping the ends together to generate a loud click. The acoustics of the species Synalpheus paraneomeris was studied by measuring the sound produced by individual shrimp housed in a small cage located 1 m from an H-52 hydrophone. Ten clicks each from 40 specimens were digitized at a 1-MHz sample rate. A low-frequency precursor signature (never reported before), which may be associated with the plunger on one of the claws that directs a water jet forward, was observed. The peak-to-peak source level varied linearly with claw size and body length and had values from 183 to 189 dB re: 1 μPa. The acoustic power produced by a typical snap was calculated to be about 3 W. A typical spectrum was very broad with only a 20-dB difference between the peak at 2–5 kHz and components out to 200 kHz.