Sound Radiation Estimate from Vibration Measurements With Multiple Cameras

This paper presents experimental results on the estimate of the sound radiation by a thin flat plate from flexural vibration measurements taken with multiple cameras. The study considers the sound radiation into free-field by a baffled rectangular plate fixed on a rigid frame. The plate is excited by a tonal point force exerted by a shaker at the first three resonance frequencies of the plate flexural response. The resulting vibration field is measured with a set of six cameras suitably synchronised. More specifically, 3D point tracking is implemented on a regular NxM grid of small circular points marked on the plate. The transverse displacements at these points are thus reconstructed from triangulation with multiple (i.e. more than 2) view-points. The transverse displacements are then used to derive the sound radiation from a direct boundary integral formulation. More specifically, for the flat rectangular plate at hand, the sound radiation is derived from the Rayleigh integral, which is approximated into a finite sum over the mesh of rectangular elements centred at the NxM grid of points depicted on the plate. The flexural vibration field and the sound radiation field derived from the camera measurements are contrasted with measurements taken with a laser vibrometer and microphone-scanner probe. The initial results presented in this paper demonstrate the feasibility of the proposed measurement approach at low audio frequencies.