The article details the experimental and numerical characterization of unit cells (UCs) designed for sound absorption using a labyrinthine pattern. The UCs exhibited a solid cylindrical design and were manufactured through 3D printing with materials ensuring mechanical compatibility. An impedance tube measured the sound absorption coefficients in accordance with international standards, allowing detailed analysis of their acoustic performance over a frequency range of 100-5000 Hz. Measurements utilized a specific setup ensuring high fidelity in capturing sound pressure and phase details, critical for evaluating sound absorption efficiency.
In order to validate the design predictions and experimentally assess the efficiency of the UC subwavelength sound wave absorption, we first perform normal incidence measurements on various types of UCs in an impedance tube.
Measurements are performed in accordance with ISO 10534-2 and ASTM E1050-19 regulations, to measure the normal incidence absorption coefficient calculated for a normally impinging pressure wave.
The impedance tube setup is depicted in Fig. 4. The impedance measurements are performed using a HW-ACT-TUBE and -STL, which has a diameter of 35 mm.
The method allows to obtain accurate sound pressure amplitude and phase measurements in the whole frequency range of interest, i.e., 100-5000 Hz, with a spectral resolution of 2 Hz.
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