PAJEWSKI, M.; SZALEWSKI, M. Ultrasonic transducers radiating into the air in the frequency range 50-250 kHz. Archives of Acoustics, [S. l.], v. 17, n. 4, p. 511–523, 2014. Disponível em: https://acoustics3.ippt.pan.pl/index.php/aa/article/view/1203. Acesso em: 13 jan. 2025.