Evaluation of the acoustic and non-acoustic properties of sound absorbing materials using a three-microphone impedance tube

TL;DR

This study demonstrates a simple indirect method using a three-microphone impedance tube to determine both acoustic and non-acoustic properties of sound absorbing porous materials, validated across four different materials.

Contribution

It introduces an indirect characterization technique to extract non-acoustic properties from acoustic measurements, enhancing material analysis methods.

Findings

Good agreement between predicted and measured acoustic behavior.

Effective extraction of non-acoustic properties from acoustic measurements.

Validation across multiple materials confirms method reliability.

Abstract

This paper presents a straightforward application of an indirect method based on a three-microphone impedance tube setup to determine the non-acoustic properties of a sound absorbing porous material. First, a three-microphone impedance tube technique is used to measure some acoustic properties of the material (i.e., sound absorption coefficient, sound transmission loss, effective density and effective bulk modulus) regarded here as an equivalent fluid. Second, an indirect characterization allows one to extract its non-acoustic properties (i.e., static airflow resistivity, tortuosity, viscous and thermal characteristic lengths) from the measured effective properties and the material open porosity. The procedure is applied to four different sound absorbing materials and results of the characterization are compared with existing direct and inverse methods. Predictions of the acoustic behavior using an equivalent fluid model and the found non-acoustic properties are in good agreement with impedance tube measurements.