Direct Measurements of Sediment Sound Speed and Attenuation in the Frequency Band of 2–8 kHz at the Target and Reverberation Experiment Site

The sediment acoustic-speed measurement system is designed to measure in situ sediment sound speed and attenuation within the surficial 3 m of sediments in the frequency band of 2-8 kHz. Measurements were carried out during the Target and Reverberation EXperiment 2013 (TREX13) off Panama City, FL, USA. During TREX13, nine deployments at five selected sites were made along the 20-m isobath, termed the main reverberation track. The sediment types at the five selected sites ranged from coarse sand to a mixture of soft mud over sand, and the measured results show a spread of 80 m/s in sediment sound speed among the different types of sediments for all frequencies. Between 2-8 kHz, about 3% dispersion was observed at the sandy sites, whereas little dispersion was observed at the sites with mud. Preliminary attenuation results show 0.5-3.3 dB/m at the sandy sites, and 0.5-1.0 dB/m at the sites with mud in the same frequency band.