Hamdan, N. I., M. H. Zainulabidin, M. Z. Kasron, A. S. Mohd Kassim, and A. E. Ismail. “Effect of Perforation Size on Sound Absorption Characteristics of Membrane Absorber”. International Journal of Integrated Engineering, Vol. 10, no. 4, Sept. 2018, https://publisher.uthm.edu.my/ojs/index.php/ijie/article/view/2335.