D. Balbonas and G. Daunys, “Simulation of Spectral Movement of Vowels using Acoustical Tube”, ELEKTRON ELEKTROTECH, vol. 96, no. 8, pp. 62–64, Oct. 2009, Accessed: Feb. 07, 2026. [Online]. Available: https://eejournal.ktu.lt/index.php/elt/article/view/9968