Abstract: The invention relates to a convertor for converting electrical vibrations into mechanical vibrations for non-destructive testing of objects, in particular bonded joints between two or more sheets or between sheets and a honey comb structure. Said convertor comprises a polycrystalline, piezo-electric disc, with mutually insulated electrodes on both head faces. The disc is secured in a supporting element by a suspension with a resilient member pressing centrally through a metal pin against the internal head face of the disc. The supporting element is movably installed into a holder such that the supporting element can be moved from a retracted position in the direction of the extended position until such a position is reached that the piezo-electrical disc is pressured against the object to be tested with a predetermined force.The invention also relates to a method for using the convertor.