Abstract:

Can the underwater ambient sound field be used to explore the oceanography of the surf zone? A preliminary examination of the ambient sound field from 1-100 kHz along the Scripps Institution of Oceanography Pier reveals two principal sound sources: breaking waves and snapping shrimp. While local wave breaking can be loud, higher-frequency sound levels within the surf zone and in rip currents are generally very quiet, confirming high-acoustic attenuation for frequencies as low as 2 kHz. Outside the surf zone, the sound field is dominated by snapping shrimp. These creatures live on the pilings (rather than free swimming), and thus present themselves as potential sound sources at distributed locations along the pier. Individual ``snaps'' are distinctive, broadband (3--100 kHz), loud, and can be tracked for over 30 m. Can these ``signals'' be used to probe the near-surf zone environment? [Work supported by ONR.]