Acoustic Characteristics of the Snapping Shrimp Sound Observed in the Coastal Sea of Korea

Abstract

The typical temporal waveforms, spectra, and water-temperature dependence of the snapping shrimp sound in the coastal sea of Korea were investigated. The peak-to-peak source levels of the snapping shrimp sound at three sites in the coastal sea, at water depths of 8, 10, and 40 m, were also investigated. The waveform and dominant frequency response band of the sound were similar to those observed under laboratory conditions. The broad peak frequency components of the normalized average snapping shrimp sound spectra measured in nine different coastal sea areas were differently determined by superposition of the peak frequency components of individual snapping shrimp spectra for the each area. The sound did not significantly affect the ambient noise level at a low seawater temperature (< 10 degrees C). The mean peak-to-peak source levels of the snapping shrimp sound at the sites with water depths of 8 and 10m were similar, with estimated values of 176 +/- 3 and 175 +/- 3 dB (re 1 mu Pa at 1 m), respectively. However, the estimated mean peak-to-peak source level at the site with a water depth of 40m was 184 +/- 2 dB (re 1 mu Pa at 1 m). The differences in the mean peak-to-peak source levels at the three sites could be caused by the differences in the ambient pressure at the sea bottoms of the sites. For water depths below 10 m, the mean peak-to-peak source levels of the snapping shrimp sound were much lower than those estimated in a previous study, in which the water depth at the experimental site was 6.1 m. On the other hand, the mean peak-to-peak source level at the site with a water depth of 40m was similar to that estimated in a previous study. This study shows that the mean peak-to-peak source levels of the snapping shrimp sound may change as water depth is largely varied. (C) 2011 The Japan Society of Applied Physics