Sound penetration into unconsolidated sand: Quantifying and predicting acoustic scattering from proud, half buried and fully buried targets in both the laboratory and littoral environments using direct measurements of sound speed in the sandy bottom.

Abstract

The impact of unconsolidated sandy bottoms on sound propagations and scattering from targets of interest is quantified with a series of experiments in both the laboratory and in littoral environments. In the laboratory, the sound speed and attenuation is well quantified and a series of proud, partially buried and fully buried scattering measurements from a variety of targets is discussed. The compressional sound speed and dispersion is important in understanding the propagation of sound into and out of sandy bottoms and the impact of scattering from buried targets both above and below the critical angle. The compressional sound speed and dispersion are important to understand and model the unconsolidated sandy bottom and to predict the impedance loading and impact to scattering signatures from targets. We will detail several laboratory and field measurements of the compressional sound speed and scattering from buried targets. Also, we will show measurements and predictions of scattering from targets in various states of burial. Propagation models will be used to predict sound propagation and scattering in the sandy bottom and will be compared to measurements of sound propagating through the sandy bottom at close and long ranges. [Work supported by ONR.]