6.1 Introduction6.2 Approximate Methods for Measurement of Velocity and Attenuation6.2.1 Measurement of Velocity and Attenuation in Isotropic Solids6.2.2 Measurement of Velocity and Attenuation in Fluids6.3 Methods of Measuring Velocity of Sound6.3.1 Interferometer Method6.3.2 Resonance Method6.3.3 “Sing-Around” Method6.3.4 Pulse-Superposition Method6.3.5 Pulse-Echo-Overlap Method6.3.6 Measurements in Materials of High Attenuation6.3.7 Measurements at High Temperatures6.3.8 Measurements at High Pressures6.3.9 Water and Other Reference Materials6.4 Low-Frequency Measurements of Elastic Moduli and Poisson’s Ratio6.4.1 Measuring Flexural and Longitudinal Resonant Frequencies of Bars6.4.2 Measuring Torsional Resonant Frequencies of Isotropic Bars6.4.3 Determining Poisson’s Ratio, Young’s Modulus, and Shear Modulus from Flexural and Torsional Resonance Data6.5 Density, Viscosity and Particle Size Measurements6.5.1 Ultrasonic Device for Quantitative Density Measurements of Slurries6.5.2 Viscosity Measurements by Ultrasonics6.5.3 Ultrasonic Diffraction Grating Spectroscopy for Particle Size and Viscosity6.5.4 Particle Size in Emulsions, Colloids, and Slurries6.6 Determining Properties of Plastics and High Polymers6.7 General Comments on Measuring Acoustical Properties of MaterialsReferences