Propagation of sound above a porous half-space

Abstract

An exact solution for the field due to a point source above a homogeneous and isotropic porous ground has been derived in terms of a single branch line integral and a pole residue. The expected properties of the porous ground lead to a less complex solution than that usual to geophysics or underwater acoustics. The method of steepest descents modified by subtraction of the pole enables the derivation of an approximate solution for an externally reacting boundary. The precise nature of the further approximations that follow the assumption of a locally reacting (or impedance) boundary is made explicit and the role of the surface wave pole is clarified. Finally, the existing solutions for a locally reacting boundary are compared, and with one exception they are shown to be identical.

Measuring Sound Absorption: Considerations on the Measurement of the Active Acoustic Power

“…This sound field model consists of as emi-free field that is bounded by ap lanar,l ocally-reacting, surface, as for instance described by Attenborough [4]. It will be referred to as the reference model hereafter.An umber of methods [5,6,7,8] assume plane wave incidence, whereas other methods consider spherical wave incidence [9,10,11,12,13,14,15,16].…”

Reflection of an acoustic line source by an impedance surface with uniform flow

“…There have been many studies of the behaviour of an infinite flat impedance surface subjected to a point source in 3D [5][6][7][8][9][10] and subjected to a line source in 2D [11][12][13][14]. None of these studies consider a mean flow.…”

“…For a point source in 3D, Attenborough et al [7], building on the work of Paul [6], performed a steepest descent analysis and found a pole that gave rise to a surface wave. For a 2D line source, Mechel [14] also found a pole that lead to a surface wave.…”

Multi-Component Acoustic Characterization of Porous Media

“…The current branch cuts are referred to as the "fundamental" branch cuts (Attenborough et al, 1980). The corresponding Riemann sheet is referred to as the "principal" Riemann sheet (van der Hijden, 1984), or the "physical" Riemann sheet (Aki & Richards, 1980).…”