Sound Propagation and Absorption in Foam: A Distributed Parameter Model

Abstract

Liquid-base foams are highly effective sound absorbers. A better understanding of the mechanisms of sound absorption in foams was sought by exploration of a mathematical model of bubble pulsation and coupling and the development of a distributed parameter mechanical analog. A solution by electric circuit analogy was thus obtained and transmission line theory used to relate the physical properties of the foams to the characteristic impedance and propagation constants of the analog transmission line. Comparison of measured physical properties of the foam with values obtained from measured acoustic impedance and propagation constants and the transmission line theory showed good agreement. We may therefore conclude that the sound propagation and absorption mechanisms in foam are accurately described by the resonant response of individual bubbles coupled to neighboring bubbles.

Heat transfer in sound propagation and attenuation through gas–liquid polyhedral foams

“…Gas-liquid foams have attracted attention for years because of their unusual physical properties and wide range of applications [1][2][3][4][5][6]. In particular, foam acoustics offers a variety of possible applications: noise-level reduction of blasts when foam fills the blast chamber, and of turbine engine exhaust by means of foam injection, foam injection; monitoring the foam drive processes for increasing the recovery of oil etc.…”

“…However, for sufficiently low sound excitation frequencies thermal dissipation may be identified as the dominant damping mechanism over the viscous friction [13,14]. The conventional cell methods [9][10][11], and the earlier distributed analog method [4] are based on the explicit hydrodynamic solution around a spherical bubble within the infinite layer of the incompressible liquid. They assume the radius of spherical cells to be much larger than the bubble size [9][10][11]14].…”