Measurement of the Frequency Dependence of the Sound Speed and Attenuation of Seafloor Sands From 1 to 400 kHz
Abstract
Measurements of sound speed and attenuation were performed over a frequency range from 1 to 400 kHz in the sandy seafloor near Ft. Walton Beach, FL, as part of the 2004 Sediment Acoustics Experiment (SAX04). The measurements at the lowest frequencies, from 1 to 20 kHz, were performed by transmitting tone burst signals from two acoustic sources positioned at depths up to 1 m below the seafloor which were recorded on a 4 m x 4 m array of 35 hydrophones emplaced to depths of between 0.1 and 1 m. Measurements were obtained at frequencies from 40 to 200 kHz with the In Situ Sediment Acoustic Measurement System (ISSAMS), a fixed linear array of four piezoelectric probes. The probes were inserted to a depth of 0.3 m, and the outer two probes were used as transmitters, with the inner probes acting as receivers. Sound-speed measurements were also made at 100, 200, and 400 kHz on diver-collected cores using four separate pairs of ultrasonic transducers. The sound-speed measurements above 40 kHz demonstrate an essentially constant sound-speed ratio with frequency of between 1.165 and 1.175, where the sound-speed ratio is the ratio of the speed through the sand to the speed through the overlying seawater. The sound-speed ratio determined from the low-frequency array data decreased from 1.135 to 1.115 with decreasing frequency below 20 kHz.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 2010
- Accession Number
- ADA529031
Entities
People
- Leonard D. Bibee
- Michael A. Zimmer
- Michael D. Richardson
Organizations
- United States Naval Research Laboratory