Measurement of the absorption coefficient in an anechoic chamber based on the subtraction method

Persistent inter-laboratory variability in sound absorption coefficient (α) measurements, particularly under the ISO 354 standard, has raised concerns regarding its reproducibility and robustness. This study introduces and critically assesses a modified measurement methodology inspired by ISO 13472-1, adapted for implementation in anechoic environments. The proposed framework incorporates an enhanced measurement configuration and a signal processing strategy based on multi-angular averaging, aimed at improving the stability of measured α and minimizing undesired effects that manifest locally. A comprehensive parametric investigation is conducted to quantify the effects of microphone distance, source location, incidence angle, and sample surface area on α. Experimental results are compared with conventional ISO 354 measurements, the impedance tube method, and numerical simulations based on the Johnson–Champoux–Allard–Lafarge (JCAL) model for rock-mineral wool. The results indicate that the proposed approach yields absorption coefficients that are comparable to those obtained through standardized methods, highlighting its strong potential for adoption as a standardized alternative or complementary technique in acoustic material characterization.