PAJEWSKI, M., and M. SZALEWSKI. “Ultrasonic Transducers Radiating into the Air in the Frequency Range 50-250 KHz”. Archives of Acoustics 17, no. 4 (May 1, 2014): 511–523. Accessed June 21, 2025. https://acoustics.ippt.pan.pl/index.php/aa/article/view/1203.