Experiments on discrimination between the same materials of different grain size

The authors devised a method to discriminate water bottom materials using the pulse echo method and multilayered neural network data processing. Using this method, experiments to investigate the discrimination ratio were carried out using crushed stones and sea sand in a water bath. In the case of crushed stones, the change in discrimination ratio due to the change in size of crushed stones was studied. For sea sand with small grain size relative to the wavelength, the change in the discrimination ratio relative to specific acoustic impedance was studied. As the result of the experiments, a discrimination ratio of 70–80% was achieved when the size of crushed stones was different by approximately one wavelength, and there was a difference of 12000 ( g/cm 2 ·s) in impedance for sea sand.