Plane wave approximation in a pulse transmission system and its application to attenuation measurements [ultrasonics]

Diffraction is a major source of error in measuring attenuation of materials with the acoustic pulse method. Experiments have shown that, in a pulse transmission system with a focused transmitter and a receiver made of a thin PVDF film of a large aperture, the received acoustic pulse can be approximated very well as a plane wave over a large range of the radiation field. Therefore, the usual required diffraction correction can be avoided in measurements. Numerical analysis is presented to show the validity of the plane wave approximation under different sizes of receiver. Computer simulation and experimental results are compared, showing good agreement. Applications, together with advantages and limitations of the system, are discussed