Unified Description of Second-Order Phenomena in Sound Waves

The generation mechanism of acoustic streaming and radiation pressure are discussed along with the KZK equation, which explains successfully the propagation of finite-amplitude sound waves. The energy loss of a sound beam in a viscous fluid generates the driving force of streaming which induces mass flow in the beam. The radiation pressure acts on the surface of an object whose acoustic impedance is different from the fluid. The effect of flow generated around the object on the radiation pressure is greater when the object is smaller. The main purpose of this paper is to describe the unified relationships among waveform distortion, acoustic streaming, and radiation pressure.