Fabrication, characterization, and application of the water hyacinth biochar-polyvinyl alcohol composite as an advantageous sound absorber material

Abstract The research was aiming to investigate the potency of water hyacinth (WH) biochar as the most advantageous sound absorber composite when it was blended with polyvinyl alcohol (PVA). It was the first time using WH biochar-based composite as a sound absorber material. Analysis and characterization of the produced WH biochar were essentially performed using N2 absorption–desorption, FTIR spectrophotometer, and SEM methods. While the capability of the sound absorber material was technically conducted using a polyvinyl chloride (PVC) impedance tube of about 95 cm in length with internal and outer diameters of about 9.5 cm and 9.8 cm respectively. The materials that would be tested for their capability of sound absorber were prepared in a disk-like form with about 9.5 cm in diameter and 0.5 cm in thickness. The sound source was continuously turned on for 2 min and transmitted wirelessly through the impedance tube, and the decreasing intensity of the sound was recorded every 5 s. The results showed that the sound absorption coefficient (SAC) of the WH biochar-PVA composite was about 6.50% (0.0650) up to 21.03% (0.2103), while the SAC of the Styrofoam was just about 4.37% (0.0437). This research concluded that the WH biochar produced by the thermal energy of 500 °C indicated it could be the best sound absorber composite when it was blended with PVA, especially for a low frequency of about 440 Hz.