Design and fabrication of low-cost impedance tube to measure the sound absorption coefficient of selected materials

Abstract

Commercial impedance tubes remain prohibitively expensive and difficult to access for many researchers and practitioners. This study created a more accessible and affordable solution to accurately measure the sound absorption coefficient of various materials by designing and fabricating a low-cost impedance tube that meets International Standard (ISO 10534-2). The experimental evaluation included tests with an empty tube and acoustic samples, such as melamine foam and glass wool. In each test, the transfer function, reflection factor, and sound absorption coefficient were then calculated from the measured complex sound pressures, showing consistent behavior expected for both the empty tube and selected materials. The variability in the results indicated that the cutting process, mounting techniques, and environmental conditions exerted a significant influence on the measurements. The low-cost fabricated impedance tube, despite its affordability (costing only 1% to 7% of commercial alternatives) proved suitable for measuring the absorption coefficient of materials.