Design and Construction of a Material Sound Absorption Testing Apparatus Based on a Simple Impedance Tube System

Abstract

Noise is an undesirable sound that can negatively affect human comfort, productivity, and health, making effective noise control an important aspect of acoustic design. One practical approach to noise control is the use of sound-absorbing materials, whose performance must be evaluated using reliable testing methods. This study aims to design and construct a sound-absorption testing device based on a simple impedance tube system and to evaluate its performance in measuring and analysing sound pressure. An experimental method was employed by comparing sound pressure levels with and without test material samples at frequencies of 125 Hz, 250 Hz, 500 Hz, and 1000 Hz. The device was constructed from a 4-inch-diameter PVC tube, 100 cm long, equipped with one speaker and two microphones using the two-microphone method. Sound pressure data were recorded with Audacity and analysed for Sound Pressure Level (SPL) to determine the sound absorption coefficient using an energy comparison approach. The results indicate that the developed device effectively detects differences in sound pressure levels between conditions with and without material samples. A significant increase in sound absorption was observed at higher frequencies, particularly at 1000 Hz, where the absorption coefficient reached 0.97, indicating near-perfect absorption. In contrast, lower frequencies showed relatively small absorption values, highlighting the frequency-dependent behaviour of the tested material (rockwool). In conclusion, the simple impedance tube system can provide reliable measurements of sound absorption characteristics. The device is suitable as a preliminary testing tool and as an educational medium in acoustics, especially for evaluating the performance of sound-absorbing materials across different frequency ranges.