Near- to far-field characterization of a parametric loudspeaker and its application in non-destructive detection of detachments in panel paintings

The particular properties of the parametric loudspeaker make this class of sources an attractive investigation tool especially for non-destructive testing (NDT). Recently actual applications mainly in the field of material's acoustical characterization are emerging. The authors present the analysis of the pressure field generated by a commercial parametric loudspeaker both in the near- and far-field, aiming at the understanding of the modality of its employment as excitation source in a measuring system. Successively the parametric source was integrated in a system purposely developed for acoustic diagnostics on objects of heritage interest. It was used in an in situ investigation on the renaissance panel painting Annunciazione by the Italian artist Benozzo Gozzoli (XV century) revealing pictorial film detachments. Preliminary results are here presented, disclosing the potential of the parametric loudspeaker for the enhancement of the spatial resolution in the acoustic measurement, of the non invasiveness of the investigation tool, and also of the operator comfort.