EXPERIMENTAL INVESTIGATIONS OF THE ACOUSTICAL PROPERTIES OF FOAMS

The velocity and absorption of sound in water-air foams with multiplicity parameters ranging from 80 to 1700 are measured. It is shown that the sound velocity in foams is independent of the frequency and increases with the multiplicity parameter in the frequency range from 100 Hz to 1000 Hz. An empirical relation is obtained for the sound absorption coefficient-alpha in the foam as a function of the sound frequency v and the multiplicity parameter of the foam K: alpha = 5.2.K-0.5.nu-0.16(m-1). When sound is transmitted through a foam layer, it is observed to undergo strong attenuation at the boundaries of the layer. The sound attenuation at the boundaries increases with increasing frequency and with increasing multiplicity parameter of the foam.