Theoretical estimation of sound absorption characteristics in a collection of rectangular holes: Comparison with experimental results

This study quantifies the sound absorption properties of small rectangular or square pores that are less than a few millimeters per side, based solely on their geometric dimensions. Analytical solutions for the sound absorption coefficient of narrow tubes with rectangular holes have not been obtained. Therefore, alternative methods of predicting the sound absorption coefficient, such as using the circular tube approximation or the two-plane approximation, are possible. In this study, the sound absorption coefficient was estimated by several theoretical models that are considered useful for estimating the sound absorption coefficient in rectangular tubes. The results were then compared with experimental values. For square holes, the accuracy of the sound absorption coefficient increased in the order of the model considering two-sided circumference only, the circular tube model, and Allard's method based on Stinson's. In rectangular holes, Allard's method based on Stinson's showed good agreement with the experimental data across a wide range of aspect ratios. For rectangular holes, the accuracy of Stinson's two-plane approximation was superior to that of the circular tube approximation when the aspect ratio was 4. Furthermore, when the aspect ratio was 8, the accuracy of Stinson's two-plane approximation became comparable to that of Allard's method based on Stinson's.