Chapter 2: Acoustic Radiation, Diffraction and Scattering

Sources of the acoustic wave are also called transducers, which can convert the other forms of energy (vibration energy, electromagnetic energy, thermal energy, etc.) to acoustic energy. They can be divided into the volume and surface sources from their geometry or the characteristic of the acoustic field of their radiation. The surface source usually is the vibrating surface of a piezoelectric solid. The acoustic field generated by the source may be treated as a boundary condition problem mathematically. When an acoustic wave propagating in a region with a sound speed encounters another region of a medium with a different sound speed whose dimensions are relatively smaller than the wavelength of the sound wave, the trajectory of the incident wave departs its original direction, this phenomenon is called the scattering. The resulting total wave due to the scattering subtracting the incident wave is called the scattered wave.