Scattering of an Underwater Ultrasonic Beam from Liquid Cylindrical Obstacles

Abstract

An ultrasonic beam (frequency, 1.145 mc/sec.; wave-length, 0.13 cm) produced in water by a quartz crystal is scattered by various liquid cylindrical obstacles (diameter, 1.3 cm). These obstacles are composed of methyl and amyl alcohols, ethyl alcohol-H2O solutions, NaCl-H2O solutions, and diethylaniline. They provide a range of values of acoustic impedance, acoustic velocity, and ratio of obstacle diameter to wave-length. Pressure amplitude distributions are measured over various cross sections of the scattered beam for a fixed position of the obstacles relative to the source. The scattered wave fronts are also obtained. These two types of measurements lead to the conclusion that the scattering is diffractive rather than ray acoustical. Other evidence is given which exhibits the presence of a scattered wave.