Reconstruction of the sound radiation field from flexural vibration measurements with multiple cameras

This paper presents the background theory and the experimental implementation of a new approach for the reconstruction of the sound radiation field produced by the flexural vibration of a distributed structure using video image acquisitions. The study is focused on tonal flexural vibration and sound radiation at the first five resonance frequencies of a baffled flat rectangular plate model-structure. The plate is divided into a regular mesh of rectangular elements whose centres are marked with small bullets. The transverse vibrations at the grid of target points are estimated via triangulation from the images acquired with six cameras unevenly spread along half of a circle located, with a small offset, parallel to the surface of the plate. The sound radiation field in free space is then reconstructed from the Rayleigh integral, which is approximated into a finite sum over the mesh of elements. Both the flexural vibration field and the sound radiation field derived from the cameras video acquisitions are contrasted with measurements taken respectively with a laser vibrometer and an array of microphones.