Effective procedure for determination of unknown vibration frequency and phase using time-averaged digital holography

Reduction of undesirable structural vibrations and of the associated structure-borne noise is a classical problem that remains important today. There are many ways of passive damping of structural vibrations. Unfortunately, most of them require addition of substantial amounts of damping materials, which is not always possible because of the mass and volume restrictions associated with structures' operational requirements. In this connection, development of new methods of vibration damping is always desirable, especially if they can avoid the mass or volume penalty. Among such new methods are those based on the Acoustic Black Hole effect (ABH), which is a topic of increasing interest in the vibroacoustic and noise control communities. In the majority of practical situations, this innovative technique for reduction of structural vibrations and of the associated noise is based on the propagation properties of flexural (bending) waves in thin structures of variable thickness. If a local thickness of a structure changes with wave propagation distance quickly enough, then such a structure may result in trapping the vibrations in the area of progressively decreasing thickness, in which a small patch of viscoelastic coating is sufficient to dissipate the localized energy very efficiently.The scientific literature on this subject has grown rapidly in recent years. In particular, a large number of research papers have been published in leading international journals

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