Investigation are performed to assess the condition of slabs, beams, columns, walls, pavements, runways, tunnels, and dams. Voids, honeycomb, cracks, delaminations and other damage in concrete, wood, stone, and masonry materials can be found utilizing the Impact Echo(IE) method. IE investigations are also performed to predict the strength of early age concrete if the member thickness is known and to measure the thickness of structural members. An advantage of the Impact Echo as opposed to the Ultrasonic Pulse Velocity(UPV) method is that only one side of the structure needs to be accessible for testing. In addition, the IE method will provide information on the depth of a flaw or defect, in addition to mapping its lateral location and extent.