Self-interference between forward and backward propagating parts of a single acoustic plate mode

Near and far fields of a particular (S-1) Lamb mode, generated on a steel plate by means of a wedge transducer, are investigated. These show an oscillating behavior of the radial profile of the acoustic field amplitude that can be interpreted and modelled as interference phenomenon between forward and backward propagating parts of the Lamb mode, simultaneously generated at the interface between transducer and plate.