Hamdan, Nur Izzah, Muhd. Hafeez Zainulabidin, Md Zainorin Kasron, Angzzas Sari Mohd Kassim, and Al Emran Ismail. 2018. “Effect of Perforation Size on Sound Absorption Characteristics of Membrane Absorber”. International Journal of Integrated Engineering 10 (4). https://penerbit.uthm.edu.my/ojs/index.php/ijie/article/view/2335.