Numerical Simulations of Ultrasonic Non Destructive Techniques of Masonry Buildings. B. Cannas 1 , S. Carcangiu *,1 G. Concu 2 , A. Fanni 1 and M. Usai 1 1 Department of Electric and Electronic Engineering, University of Cagliari, Piazza d’Armi, 09123 Cagliari, Italy 2 Department of Structural and Infrastructural Engineering and Geomatics, Piazza d’Armi, 09123 Cagliari, Italy *Corresponding author: Piazza d’Armi, 09123 Cagliari, Italy; s.carcangiu@diee.unica.it Abstract: An experimental program has been developed, with the purpose of evaluating the reliability in building diagnosis and characterization of an integrated analysis of several parameters related to several acoustic parameters, associated with acoustic waves propagating through the material. The Direct Transmission Technique has been applied. In this paper we developed a numerical model, with the Finite Element Method, using the Transient Acoustics-Piezoelectric Interaction application mode of COMSOL. The analysis has been carried out on a model of trachite stone masonry with an inside cavity. The time travels associated with acoustic waves propagating through some sections of the considered models have been analyzed to tune COMSOL applications in order to detect the presence of the central cavity. The comparison of the obtained results with those supplied by experimental tests has been performed. Keywords: Ultrasonic wave, Non-Destructive Testing, signal processing, Acoustic analysis, Piezoelectric transducer. 1. Introduction Building preservation and restoration is a complex problem to deal with, especially when concerning building of historical relevance. The evaluation of a structure real state shouldn’t interfere with the condition and the functionality of the building, and should possibly involve limited costs. Thus, inspection and monitoring of structural conditions is becoming an essential part of proper management of buildings rehabilitation. In the field of assessment methodologies, particular importance is given to developments of Non-Destructive Techniques (NDTs), including automated procedures and information technology to support decision making and evaluation of data. NDTs aspire to achieve the higher number of information about materials and structures without altering their condition, for example by extracting samples. Thus, the ageing of building heritage and the need of guarantee its safety, especially when reconstruction of its past life and previous restorations is not clear, has led to the creation, the evolution and the rapid diffusion of those type of methodologies, in order to proper manage buildings rehabilitation. In fact, every work must be preceded by careful observation of the effective state of the building so as to ascertain the nature of possible structural inadequacies and be able to proceed with works that are suitable and sufficient for the rehabilitation of the building and its characteristics. An experimental program has been started with the purpose of evaluating the reliability in masonry diagnosis and characterization of the integrated analysis of several parameters associated with acoustic waves propagating through the material. Experimental tests are based on ultrasonic techniques. In this paper the finite element method is applied to the problem of non destructive testing. This is one possible way to visualize the real acoustic wave propagation into the structure. The present work has an objective to obtain a reliable numerical model of generation and reception of the ultrasonic waves through piezoelectric transducers, using the finite element method. To validate the model, experimental measurements were carried out using the equipment PUNDIT (Portable Ultrasonic Nondestructive Digital Indicating Tester), manufactured by CNS Farnell of London [1]. PUNDIT allows online data acquisition, waveform analysis and full remote control of all transmission parameters. Furthermore, his measuring device has the advantage of providing to emitter transducer a signal high enough not to necessitate the use of an amplifier. The emitter and receiver are transducers that consist of lead zirconate titanate (PTZ4) ceramic piezo electric elements in stainless steel cases with a natural frequency of 54 kHz. The emitter is connected to the Excerpt from the Proceedings of the 2011 COMSOL Conference in Stuttgart