An examination of the parameters that govern the acoustic behavior of sea bed sediments containing gas bubbles

The acoustic properties of sea bed sediments containing occluded gas are do minated by the volume of gas contained in bubbles, the size of bubbles, and the elastic properties of the soil matrix. This study evaluated current th eory developed by Anderson and Hampton to determine the sound speed and res onance frequency of gassy soils, and the models they used to determine the elastic properties of the soils. It compared calculated sound speeds, based on material properties simulated by the models, with measured sound speeds on "large bubble" laboratory soils produced in a similar manner to natural sea bed gassy soils. There was some evidence that the Anderson and Hampton equations accurately predicted sound speed at lower frequencies of bubbles resonance and below, but results were sensitive to inappropriate values fo r the elastic and damping properties of the soil. The bounds of sound speed based on the elastic properties of models that simulate " fluid" or "suspe nsion" behavior were grossly misleading when applied to large bubble soils. Conversely, sound speed based on models that correctly simulate the "bulk" or "matrix" properties of large bubble soils, at strain magnitudes and str ain rates equivalent to acoustic signals, agreed well with measured data. ( C) 2001 Acoustical Society of America.