Propagation of Sound in Porous Media : Modelling Sound Absorbing Materials

This book has grown out of the research activities of the author in the fields of sound propagation in porous media and modelling of acoustic materials. It is assumed that the reader has a background of advanced calculus, including an introduction to differential equations, complex variables and matrix algebra. A prior exposure to theory of elasticity would be advantageous. Chapters 1-3 deal with sound propagation of plane waves in solids and fluids, and the topics of acoustic impedance and reflection coefficient are given a large emphasis. The topic of flow resistivity is presented in Chapter 2. Chapter 4 deals with sound propagation in porous materials having cylindrical pores. The topics of effective density, and of tortuosity, are presented. The thermal exchanges between the frame and the fluid, and the behaviour of the bulk modulus of the fluid, are described in this simple context. Chapter 5 is concerned with sound propagation in other porous materials, and the recent notions of characteristic dimensions, which describe thermal exchanges and the viscous forces at high frequencies, are introduced. In Chapter 6, the case of porous media having an elastic frame is considered in the context of Biot theory, where new topics described in Chapter 5 have been included. Front Matter....Pages i-xiii Plane Waves in Isotropic Fluids and Solids....Pages 1-15 Acoustic Impedance at Normal Incidence of Fluids, and Highly Porous Materials....Pages 16-30 Acoustic Impedance at Oblique Incidence in Fluids, and Highly Porous Materials....Pages 31-47 Sound Propagation in Cylindrical Tubes and Porous Materials Having Cylindrical Pores....Pages 48-78 Sound Propagation in Porous Materials Having a Rigid Frame....Pages 79-117 Biot Theory of Sound Propagation in Porous Materials Having an Elastic Frame....Pages 118-144 Prediction of Surface Impedance and Sound Transmission for Multilayered Porous Media....Pages 145-185 Acoustic Field Created by Monopole and Dipole Sources in the Presence of Porous Layers....Pages 186-206 Methods of Measuring the Acoustic Impedance....Pages 207-219 Porous Materials with Perforated Facings....Pages 220-253 Impedance and Admittance Matrices, Sound Transmission Through Layered Porous Media and Reciprocity....Pages 254-277 Back Matter....Pages 279-284