Underwater sound measurements of high frequency sonars using a seabedmounted recorder

Graham Warner, Andrew McCrodan, Jeff MacDonnell, Eric Lumsden

Abstract


The regulatory permit for Statoil USA E&P Inc.'s 2011 marine survey program in the Alaskan Chukchi Sea required underwater sound measurements of high and low frequency sound sources used in the program. A seabed-mounted Autonomous Multichannel Acoustic Recorder (AMAR) was used to accurately measure high frequency sonar sound levels. The AMAR recorded 16 bit samples at 687.5 kHz for 27 hours. Sound levels from in- and out-of-beam pulses were back-propagated using spherical spreading and absorption loss at the center frequency. Sonar pulses were detected on all five track lines for the side-scan sonar, lines offset 0, 50, and 100 m for the multibeam sonar, and lines offset 0 and 50 m for the single-beam sonar. Received levels were back-propagated to estimate source level versus angle off broadside for the side-scan and multibeam sonars and versus angle off vertical for the single-beam sonar.

Keywords


Acoustic variables measurement; Architectural acoustics; Underwater acoustics; Absorption loss; Center frequency; Chukchi Sea; High frequency sonar; Low-frequency sounds; Marine survey; Multi-channel; Multibeam sonar; Single-beam; Sound level; Source level; Statoil

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