Infrared thermography is a powerful, fast and non contact method for non destructive testing of materials, based on heat conduction. While techniques like pulse or lockin thermography are based on external heat sources, other thermographic techniques, like vibro-lockin thermography, use internal sources of heat, where loss angle effect is involved. One advantage of these latter techniques is that some material features are selectively heated, so that the interpretation of the image can be straightforward. Another advantage is that the heat is generated directly on the defect, allowing to reach greater depths. Some interesting examples of thermographic inspection using ultrasonic heating source are here illustrated.