Characteristics of marine seismic survey sounds in the Beaufort Sea

Publisher Website
Google Scholar
Abstract
Geophysical survey vessels emit very intense pulses of underwater sound at intervals of several seconds; these noise pulses are sometimes detectable at very long ranges. Sound pulses from geophysical surveys were recorded in shallow parts of the Beaufort Sea during August and September of 1980–1984. Hydrophones deployed from a quiet boat were the primary sensors, but aircraft‐deployed sonobuoys were also used. Water depths for the boat‐recorded data were 9–130 m, but mostly 4 km, best‐fit equations for maximum (rms) received levels in dB generally were obtained by assuming cylindrical spreading [−10*log(range)] and a term linear in range corresponding to an absorption loss or scattering term. The coefficients of the linear term varied from −0.61 to −2.33 dB/km, increasing in magnitude for shallower water. Pulses received at ranges greater than 3–4 km were usually 0.25–0.75 s long. These pulses often began with a bottom‐traveling wave whose energy was concentrated below 100 Hz. The waterborne energy showed the geometrical dispersion that results from the summation of many sound rays that are reflected between the surface and the bottom: high frequencies (generally below 500 Hz) arrived first, followed by gradually lower frequencies. The result was a down‐frequency chirplike sound. At short ranges the signal energy was concentrated at frequencies below 100 Hz. The reactions of bowhead whales to these signals are described in a companion article [Richardson e t a l., J. Acoust. Soc. Am. 7 9, 117–1128 (1986)].

This publication has 0 references indexed in Scilit: