Design and experimental validation of a ventilated ring-type acoustic metamaterial panel for simultaneous noise reduction and airflow

While conventional closed noise barriers suffer from excessive weight and a lack of ventilation, ventilated panels overcome these limitations by allowing airflow to reduce both structural weight and wind loads. Accordingly, this study investigates a method to enhance noise reduction performance while minimizing weight, utilizing a simple cylindrical model. A fundamental cylindrical geometry was selected due to its simplicity, which facilitates fabrication, and its effectiveness in designing internal hollow structures for noise attenuation. Based on this concept, a cylindrical meta-panel was designed featuring a double-ring internal structure—comprising a large and a small cylinder—within a square lattice. To optimize the design, the effects of various parameters, such as the diameter of the inner cylinders and the orientation of the holes, on noise reduction performance were analyzed. Additionally, fluid dynamics analysis was conducted to verify that the structure allows for sufficient airflow while maintaining noise reduction capabilities. Following numerical validation, experimental verification was conducted using physical prototypes. Acrylic specimens based on the optimized geometry were fabricated and installed in a reverberation chamber to measure transmission loss. The experimental results demonstrated a noise reduction generally ranging from 15 to 28 dB, maintaining over 15 dB even in the low-frequency range below 500 Hz. These findings confirm that the proposed cylindrical meta-panel achieves significant noise attenuation despite its lightweight and ventilated design. This study is expected to serve as a foundation for the practical application of ventilated noise barriers in real-world environments.