Estimation of locally reacting surface impedance at modal frequencies using an eigenvalue approximation technique

The accuracy of computational models for acoustics is often limited by a lack of reliable information concerning the frequency-dependent impedance of surface materials. This lack of information stems from the unavailability of reliable measurement methods for low frequencies. In this work, an approach is proposed, using eigenvalue analysis, for estimating the locally reacting, frequency-dependent impedance of a sound-absorbing sample. In particular, an eigenvalue approximation method is proposed and used in tandem with an optimization routine to obtain surface impedance estimates of an installed sample at modal frequencies. It is shown, using finite element simulations of an impedance tube and a small reverberation room, that the proposed method can provide reasonable estimates of the surface impedance of a sample placed on a boundary surface.(c) 2021 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

This study proposes a method for estimating the frequency-dependent impedance of sound-absorbing materials using eigenvalue analysis. By combining an eigenvalue approximation method with an optimization routine, surface impedance estimates of installed samples at modal frequencies can be obtained. Finite element simulations demonstrate that the proposed method can provide reasonable estimates of surface impedance for samples placed on boundary surfaces.