Visco-inertial absorption in dilute suspensions of irregular particles

The presence of mineral particles in suspension results in excess acoustic attenuation which may be significant for high-frequency (tens to hundreds of kilohertz) sonar systems operating in shallow water. Laboratory measurements of absorption at 50-150 kHz in dilute suspensions of spherical, highly non-spherical and natural marine sediment particles are presented and compared with predictions of models for visco-inertial absorption by spherical and spheroidal particles. The methods are validated by the good agreement obtained between the predictions of the spherical model and measurements made with glass spheres. Good agreement is obtained between measurements with plate-like kaolin particles and the predictions of the model for oblate spheroids. Both the spherical and spheroidal models give the approximate magnitude of the attenuation in suspensions of natural marine sediment particles over the frequency range of the measurements.