M. MEISSNER, “Effect of cross-sectional area discontinuities in closed hard-walled ducts on frequency of longitudinal modes”, Arch. Acoust., vol. 35, no. 3, pp. 421–435, Sep. 2010, Accessed: Mar. 04, 2026. [Online]. Available: https://acoustics.ippt.gov.pl/index.php/aa/article/view/234