Vibration damping materials play an increasing role in environmental protection and mechanical design. Specially developed resins with optimized properties for noise abatement applications are used with success. As most metals have low internal losses, large amplitudes may be obtained in resonance modes when they are vibrated. The application of coatings of damping material with large internal damping in single layer or sandwich constructions has proved very effective in “deadening” noisy structures. A direct consequence of these developments is a great need for an objective damping measuring technique. The intersting viscoelastic properties are the density and the complex modulus of elasticity of the materialsĒ = E′ + jE″ (j =−1)and the complex shear modulusḠ = G′ + jG″. AsĒandḠare closely related through the Poisson ratio, the measurement of the complex modulus of elasticity will do. The real partE′ represents the dynamic stiffness which is the storage modulus representing the energy stored in the material during oscillation, the normally used term is dynamic modulus of elasticity. The imaginary partE″ is a measure of the loss modulus representing the energy losses. The loss factor isd=E″/E′. The viscoelastic properties may be measured through an experimental setup using standardized samples mounted in a well defined fashion and brought into oscillatory motion. The dependency on temperature and frequency may be determined in this experimental setup which is standardized in DIN 53440, pp. 1–3. Considerable experience with this method has been gained over twenty years. The method was pioneered by the late Dr. Hermann Oberst.