Acoustic black hole combined with microperforated plate for a rectangular waveguide

The concept of an acoustic black hole (ABH) for anechoic termination of waveguides has been well-established and extensively studied. The fundamental principle underlying an ABH is the deceleration of acoustic waves, leading to the accumulation and subsequent absorption of acoustic energy within the thermoviscous boundary layer formed along the ribs forming its internal structure. The primary advantage of ABHs, in contrast to classical solutions, lies in their avoidance of porous or fibrous materials, rendering them suitable for deployment in challenging environments. While the majority of published works have focused on ABHs with circular cross-sections, recent advancements have demonstrated the effectiveness of the ABH effect also in waveguides with rectangular cross-sections. However, it has been revealed that these ABHs require very fine internal structure for optimal performance, posing challenges in manufacturing. This study addresses this issue by utilizing a microperforated plate to provide the necessary resistance. To model these ABHs, a simple mathematical model is proposed, enabling the optimization of their parameters. Subsequently, their performance is investigated through numerical experiments. The validity of the results is confirmed by comparing them with a detailed mathematical model, ensuring the accuracy and reliability of the proposed approach.