Physical Acoustics V6

Book excerpt: Physical Acoustics: Principles and Methods, Volume VI provides five chapters covering the whole of physical acoustics. The first chapter extends the methods for studying high frequency sound waves in the hypersonic range by the technique of Brillouin scattering. The next chapter discusses the acoustic properties of materials of the perovskite structure. These materials have ""soft"" modes, which are transverse optic modes of the phonon spectrum that have unusually low and strongly temperature dependent frequencies. This chapter expounds the influence of the soft modes, with particular attention to potassium tantalate and strontium titanate. The third chapter gives a theoretical treatment of the properties and possibilities of surface waves in crystals that are becoming of increasing interest for delay lines, amplifiers of sound waves, and other practical applications. The fourth chapter discusses the experimental methods and results of the dynamic shear properties of solvents and polystyrene solutions from 20 to 300 MHz, including a description of its materials and steady-flow properties. The final chapter deals with condensed helium, which requires quantum reactions to account for its properties. While the experimental data on solid helium are still insufficient, this chapter gives both a theoretical and an experimental account of sound propagation in solid helium, including various liquid forms. This book is recommended to both students and physicists conducting research on physical acoustics.