Absorption of Sound in Sediments of Small Particles in Liquids

Abstract

The absorption of sound in sediments of particles in different liquids is investigated as the particle size is varied. A pulse method is used at a constant frequency of 1 Mc/s. The sediments consist of small glass spheres of uniform size, eight different particle sizes in the range from 0.0035 cm to 0.016 cm radius being used in each liquid. The liquids used are water, carbon tetrachloride, benzene and castor oil. It is found that in all cases the absorption coefficient can be represented by an expression of the form 2? = k1a3 + k2/a + k3/a2 where k1, k2 and k3 are constants which vary with the liquid used. Some support for an equation of this form is obtained from Sewell's equation applicable to particles suspended in a fluid. At large particle sizes the most important term is k1a3 which is due to scattering losses whereas at small particle sizes the last two terms due to viscous losses predominate. Where the k3 term is significant it is found to be negative, the viscous absorption rising to a maximum and decreasing sharply as the particle size diminishes.