Nondestructive and non-intrusive methods are being developed to detect voids, hidden cracks, and fine fractures in wooden art objects. Such anomalies are often the cause of premature failure. The transportation of panel paintings (paintings on wood) is an area where new techniques are needed. In particular, determining the physical integrity and baseline characteristics of art objects is critical to deciding whether they can be transported to exhibitions. Air-coupled ultrasonics is a nondestructive evaluation technique that may be useful for establishing the structural integrity of panel paintings. Traditional ultrasonic methods require the use of coupling liquids such as water, oil, and grease. The advantages of using other, non-contact ultrasonic methods in the art conservation field are obvious. The me1hod has advantages over radiography for finding cracks at certain angles in the wood and delaminations between layers of a painting. Also, unlike radiographic techniques, ultrasonics does not present a health hazard. The air-coupled system currently under development at the Johns Hopkins University, is especially configured to allow investigations of wooden panels. The system is capable of producing two-dimensional representations (C-scans) of a panel painting. Special signal processing methods are used to inspect inhomogeneous materials such as wood. In particular, methods are being developed to enable the system co distinguish potentially harmful anomalies from inhomogeneities natural to wood, including growth rings.