“…[18 ], by Maheshwari et al , presents hollow cone attachments coupled with conventional ultrasonic transducers for achieving subwavelength resolution imaging at a relatively higher speed and minimal cost, while Kumar, Shakya and Goswami demonstrate the optimal frequency combination estimation for accurate ultrasound non‐destructive testing for an object with a heterogeneous inner profile in [19 ]. In [20 ], Sikundalapuram et al , present an elastic metamaterial rod for mode filtering in ultrasonic applications.…”