Increased use of advanced materials and more stringent requirements for process and quality control are creating new needs for nondestructive inspection techniques. Ultrasonics is a widely used technique for defect detection in various materials and is being developed, and even in some cases actually applied for microstructural characterization. However, ultrasonics in its present state of implementation in industry suffers several limitations. Probing materials at elevated temperature is made difficult by fluid coupling problems. Inspecting specimens of complex shapes requires sophisticated robotic manipulators to properly orient the transducer. Furthermore, since the technique relies on a piezoelectric resonator to generate and receive ultrasound, it does not have the adequate bandwidth or sensitivity for some applications.