Although research on cross-laminated timber (CLT) has been extensively investigated, its sound absorption characteristics in relation to CLT’s structure are still sparse in the literature. This study examined the influence of wood species, density, and edge gaps on the sound absorption performance of single or hybrid species of CLT. Six three-layer CLT configurations were fabricated using rubberwood (600–700 kg/m3) and coconut wood of two density ranges (600–700 kg/m3 and 700–800 kg/m3). Three types of edge gaps were introduced—between major laminations, between cross laminations, and a combination of both—at widths of approximately 6, 12, and 18 mm. Sound absorption was strongly affected by wood density, species, and their placement within the CLT structure. Panels incorporating high-density coconut wood showed improved low-frequency absorption, while low-density coconut layers enhanced high-frequency absorption due to their parenchyma-rich microstructure. In addition, performance varied according to gap type and frequency. Core gaps reduced sound absorption across most frequencies, whereas gaps between major laminations improved absorption at low and high frequencies through diffraction and increased surface area. Smaller gap widths further enhanced performance. Panels with combined gap types demonstrated superior absorption compared with those containing a single gap type or no gaps.
Srivaro et al. (Sun,) studied this question.