MAKAREWICZ, Rufin, and Gabriela KERBER. “A Method for Determining the Equivalent Level of Noise Generated by a System of Sources in an Enclosure”. Archives of Acoustics, vol. 7, no. 3-4, Mar. 2016, pp. 183-96, https://acoustics3.ippt.pan.pl/index.php/aa/article/view/3281.