Based on the relationship between resonance and tension on thin sheets, an experimental approach was adopted to test the slow dynamic behaviour of Paper, Low Density Polyethylene (LDPE), the laminate of both and same laminate with Aluminium inclusive. We used a non contact acoustic excitation and non contact laser sensing. We chose to use a non contact acoustic excitation for its efficiency. A mixed dynamic extension was applied to the specimens including periods of dynamic extension and a long time of constant extension (conditioning). The modal parameters were extracted via a laser vibrometer using the LabVIEW software. The results enabled us to show the slow dynamic characteristics of the thin sheets.