Study of the calibration method of pressure-velocity probes and its application in a field of progressive plane waves

This dissertation presents a calibration procedure for pressure-velocity probes. The dissertation is divided into four main chapters.The first chapter contains six main sections. In sections 1 and 2, the wave equation in fluids and the sound speed in gases are calculated; the third section contains a general solution of the wave equation in the case of plane acoustic waves. Section four and five introduce the definition of the acoustic impedance and admittance, and the practical units the sound levels are measured with, i.e. the decibel scale for pressure, velocity, impedance and intensity. Finally, the last section of the first chapter reports about the standard frequency-band analysis of a sound wave, the discrete Fourier analysis including the definition of some important functions such as the cross spectrum and the transfer function, which have been used for the calibration. The second chapter describes various reference field calibration procedures that are currently used to calibrate P-V probes. In particular the progressive plane wave method, which is the one which has been used in this work. A short description of the working principles of the twotransducers that have been used, with a focus on the velocity one, has been also reported.The third chapter of the dissertation is devoted to the explanation of the calibration set up, the instruments used for the data acquisition and analysis, and the software routines which have been used for the calibration process. This chapter concludes by reporting in detail results of the implemented calibration and data analysis.Finally conclusions and future applications are reported in the last chapter.