A resonator installed in a wooden puzzle board greatly enhances sound absorption capability at low frequency: A new approach

Abstract

Loud noise has become a regular part of life due to growing urbanization and lifestyle changes, making noise pollution a severe health concern. However, eco-friendly materials for low-frequency sound absorption still need improvement. Wooden puzzle-assembled boards are being used to construct wooden buildings in South Korea, but they require better sound absorption performance. Therefore, we have developed a strategy to enhance the sound absorption capability of wooden puzzle-assembled boards by suggesting the installation of a single-frequency resonator on the board. The resonator contains nine pinholes with a 6 mm diameter perforation connected to a 30 mm diameter hole leading to the center hollowed cavity (CHC). We evaluated the sound absorption coefficient (SAC) of the control (i.e., cross-laminated timber (CLT)) and a resonator board. The SAC of the resonator with zero pinholes (i.e., CHC), one pinhole (PH-1), five pinholes (PH-5), and nine pinholes (PH-9) were estimated using a two-microphone transfer function method at low frequencies ranging from 100 to 1600 Hz. The average SAC of PH-9 showed significant improvement at the frequency of 450 Hz (0.637 ± 0.001; 818%) compared to the control samples. The noise reduction coefficient was improved by 239% (0.07 for the control and 0.23 for the PH-9). We compared the experimental results in this study with theoretical results and found that the orientation of the neck length significantly impacted the resonant frequency of the pinhole resonator. This finding provides valuable insights into the design and optimization of pinhole resonators for specific acoustic applications.