Experimental Investigation of Ultrasound Wave Focusing in Attenuative Solids

This paper presents an experimental study on ultrasonic focusing in an attenuative solid made of cement mortar. The objective is to comparatively investigate the performance of various techniques for wave focusing. Standard attenuation measurements are performed on small cement mortar samples to generate a preliminary idea about the loss in the material. Subsequently, focusing experiments are conducted on a larger mortar block fabricated with the same mix design parameters. The time-delayed and time-reversal methods are employed to perform focusing. A synthetic aperture approach is used to generate the unfocused and focused fields. The time-reversal focusing method generates a narrower focal spot in comparison to the time-delayed method, indicating better focusing action. The experimental results are also compared with an analytical model of focusing in an attenuative fluid with an array of point sources, and a good agreement is confirmed.