Statistical dispersion of effective acoustic parameters and airflow resistivity of porous absorbers using the two-thickness method in an impedance tube

Mitigating noise pollution is essential for enhancing acoustic comfort in industrial, residential, and urban environments. Porous materials, such as open-cell foams and fibrous materials, are widely used in noise control applications. Their effectiveness depends on accurately determining macroscopic properties like airflow resistivity, porosity, and tortuosity. Traditional direct methods require dedicated experimental setups, making them costly and time-consuming. This study presents an efficient approach based on ISO 10534-2 standard, employing the two-thickness method in an impedance tube. By measuring surface impedance and sound absorption for two thicknesses, the complex wavenumber and characteristic impedance are derived in a single experiment. These parameters facilitate finite element acoustic simulations under the equivalent fluid model, providing advantages over surface impedance-based approaches. A key contribution is the statistical analysis of data dispersion, focusing on obtaining airflow resistivity. The mean values and confidence intervals of melamine foam and fiber wool parameters are assessed, thereby enhancing the reliability of the results. This analysis, based upon repeated measurements, ensures robust material characterization. The proposed method provides accurate acoustic parameters while reducing experimental time and costs, making it suitable for laboratories with limited resources. Ultimately, the statistical approach to multiple samples addresses a gap in porous material characterization research.