01841nas a2200229   4500000000100000000000100001008004100002260000800043653002900051653002700080653001700107653001400124653002100138100001500159700002000174700001800194245009400212856004000306300001200346490000800358520124500366       2001                            d  bASA10aacoustic wave absorption10aacoustic wave velocity10aoceanography10asediments10aunderwater sound1 aAngus Best1 aQuentin Huggett1 aAndrew Harris00aComparison of in situ and laboratory acoustic measurements on Lough Hyne marine sediments  uhttp://dx.doi.org/10.1121/1.1382616  a695-7090 v1103 aCompressional wave velocity and attenuation were measured at frequencies of 200\textendash1500 Hz on seafloor sediments at Lough Hyne, Ireland, using a mini-boomer source and hydrophone array. Velocity and attenuation were also measured in the laboratory at 200\textendash800 kHz on a 1 m long sediment core taken from the site. The in situ results indicate an average sediment phase velocity of about 1600 m/s and sediment quality factor of 10\textendash20. The laboratory core measurements give an average phase velocity of 1793\textpm26 m/s and quality factor of 16\textpm5. The poorly sorted, Lough Hyne sediments are highly attenuating and highly dispersive when compared to values published in the literature for well-sorted, marine sediments such as clean sands and marine clays. The results are consistent with the few published data for poorly sorted sediments, and indicate that intrinsic attenuation is highest when the mass ratio of mud (clay+silt) to sand grade particles is close to unity. It is proposed that compliance heterogeneities are most abundant when mud and sand grade particles are present in roughly equal proportions, and that the observations support local viscous fluid flow as the most likely loss mechanism.