Methods are presented. Signals are sent into a first surface of a structure using an ultrasonic transducer. Ultrasound response signals are received at the ultrasonic transducer. A portion of a second surface of the structure is heated while the ultrasonic transducer is sending signals into the first surface, wherein the second surface is on an opposite side of the structure from the first surface. Infrared images of the portion of the second surface of the structure are taken after heating the second surface.