The tymbal of Cyclochilca australasiae has a posterior plate, with anterior alternating short and long tymbal ribs joined together by sheets of resilin. The tymbal muscle acts on the tymbal plate causing the ribs to buckle inwards in sequence. As it buckles, each rib deforms from a convex to a V-shaped profile. The maximum vibration during the inwards buckling occurs at the V at the middle of the long ribs; the ribs vibrate in this region when driven by sound. After the tymbal has buckled outwards, the whole tymbal rib surface vibrates at around 6 kHz. Inward-going tymbal clicks produce a sound frequency of 4 to 4.5 kHz, which is a dominant frequency of the insect's song, and outward-going clicks produce 5.5 to 6.5 kHz. The resonant frequency of the tymbal changed from 5.5 kHz when buckled out and to 4.3 kHz when buckled in. The tymbal appears to be the primary resonator determining dominant frequency in the insect's song and provides a pressure drive inside the insect's abdomen. The abdomen acts as an acoustic load to the tymbals, resonant at the same frequency, and providing acoustic matching between the tymbals and the surrounding air.