COMPARISON CALIBRATION OF LOW-COST PROTOTYPES OF ACOUSTIC PRESSURE-VELOCITY PROBES AND SOME APPLICATION CASE-STUDIES

The main topic of this work is the acoustical characterisation and the comparison calibration of a new low cost prototype of a pressure-velocity probe based on MEMS and CMOS technologies. The development during the last years of micro sensors using the double hot-wire anemometric transduction principle, has permitted to directly measure the velocity of the air particle, thus giving a fundamental contribution to the intensimetric measurements. This in turn required a more deep study of the calibration techniques as at least two acoustical signals (pressure and axial velocity) have to be processed simultaneously in order to obtain precise and affordable measurements of energetic properties of sound. In particular this work is devoted to the analysis and experimental validation of the "comparison calibration" methodology when applied to pressure-velocity probes still in their early stage of prototypes. After an introduction on the Acoustical Energetics, in which the main quantities are described and simulated for a monochromatic field, the next chapters are dedicated to the probe realised within the SIHT (Sogliano Industrial High Technology) project, which is based on the collaboration between the Institute of Acoustics and Sensors Corbino-CNR, of the CNR-IEIIT and of the Deltatech industry in Sogliano al Rubicone (FC, Italy). We describe the different prototypes that have been realised and their relative characterization, that have been useful to design new and improved prototypes. The particular geometry of the prototypes has also required a new procedure of comparison calibration, in which the probe under test is calibrated using a reference one, in a generic field. The possible applications of the new probe are various, and go from audiometric field to condition monitoring, and are investigated in the last chapter.