Elucidation of a mechanism of acoustic impedance technique using two cardioid microphones and ensemble averaging method

Abstract

Recently, there is growing need for in-situ impedance measurement of several materials. We propose using two cardioid microphones (called C-C sensor) for it. C-C sensor has many advantages against two omnidirectional microphones (called P-P sensor) and one omnidirectional microphone and sound velocity (called P-U sensor). I reported the possibility of using C-C sensor for measuring acoustic impedance on 12th Western Pacific Acoustics Conference 2015 (WESPAC2015) and International Congress on Acoustics 2016 (ICA2016). When measuring some porous materials, C-C method can measure acoustic impedance as same as using P-P method, and C-C method can do it from 100 Hz to over 10 kHz. Next, we tried to elucidate the mechanism of using C-C sensor and Ensemble Averaging (EA) method using numerical experiments. As a result, the range in application of C-C sensor for measuring acoustic impedance was clarified. In this presentation, we'll introduce the measuring technique and mechanism.