Design of a Phase Calibrator to Evaluate Non-Matched Microphones for Intensity Probes

Abstract

Intensity measurements represent a well-established method to determine the sound power of an emitting object. The principal strength of this technique relies upon the possibility of performing the measurements in situ, with no special required conditions concerning the surrounding sound field. Commercially available sound intensity probes rely on two phase-matched microphones properly spaced concerning the desired frequency range. Given the physical and mathematical principles behind the intensity method, phase differences between the signals assume a crucial role. This report aims to study the possibility of designing a cost-effective acoustic phase calibrator to extract the intrinsic phase mismatch of standard class-1 microphones. A phase calibrator has been designed to identify phase mismatches between the microphones and provide the required corrections at specific frequencies. Numerical acoustical Finite Element Method (FEM). models of the calibrator configurations have been implemented. The results of the numerical models have lately led to three calibrator prototypes that have been produced by 3D-printing and tested. They have shown good results when compared to a commercially available and much more expensive acoustic coupler.

Keywords

• sound intensity probe
• acoustic phase calibrator
• microphones
• phase difference