A contact-less diagnosis system for frescoes. Part two: Acoustic excitation–acoustic response

This paper presents a significantly modified technique with respect to the previous paper (Collini L, Garziera R, Mangiavacca F. Development, experimental validation and tuning of a contactless technique for the health monitoring of antique frescoes. NDT&E Int 2011;44(2):152–157 [4]), which described an NDT for the diagnosis of antique fresco paintings based on the laser measurement of the fresco's detached areas. In this paper, we replace the laser measurement by an acoustic measurement, developing a measuring technique based on the principle “acoustic excitation–acoustic acquisition”. Replacing the laser with an acoustic device has a great advantage due to the low cost of the sensors, but the drawback is the need for a more accurate and sophisticated tuning process.