Purwanto, B., M. H. Aryantie, Z. Zulfachmi, and R. Aprishanty. “Low-Cost and Portable Sound Reduction Box: Innovation for Acoustic Material Performance Measurement”. Journal of Engineering and Technological Sciences, vol. 52, no. 5, Sept. 2020, pp. 732-44, doi:10.5614/j.eng.technol.sci.2020.52.5.9.