This part of ISO 6721 specifies a bending-vibration method based upon resonance curves for determining the flexural complex modulus E*f of homogeneous plastics and the damping properties of laminated plastics intended for acoustic insulation, for example systems consisting of a metal sheet coated with a damping layer, or sandwich systems consisting of two sheet-metal layers with an intermediate plastic layer. For many purposes it is useful to determine these properties as a function of temperature and frequency.