Acoustic seminar | 08 June 2023

In nondestructive evaluation and medical fields, sound waves are employed to noninvasively detect cracks and abnormal cells. However, the presence of a significant impedance difference between different mediums results in a limited amount of energy reaching the target, leading to reduced image quality and detection efficiency. While quarter wave matching layers have effectively facilitated sound wave transmission at specific frequencies, the requirement of multiple layers for broader bandwidth poses challenges due to limitations in thickness. Recent advancements in acoustic metamaterials, characterized by their subwavelength dimensions and unique properties such as negative density and bulk modulus, have shown promise for such applications. Nevertheless, their bandwidth remains limited due to impedance mismatch with the background medium, which limit their practical applications. In this talk, I will discuss two approaches utilizing metamaterials to enhance impedance matching. The first approach involves using a complementary acoustic metamaterial, which exhibits negative material properties, while the second approach utilizes chiral shaped metamaterial that employs a coiled-up space structure. Finally, I will demonstrate the working mechanisms and applications of these approaches in enhancing transmission through a skull layer.