Fig. 9. Envelopes of mechanical deflections along the tympanal ridge. Top: for a 10 kHz driving frequency (calling song dominant frequency), deflections are shown for phase increments of 10° in the full oscillation cycle. Minimal and maximal values are plotted in red. Bottom: minimal and maximal deflection shapes for different driving frequencies: 5 kHz (black), 10 kHz (red), 15 kHz (green), 20 kHz (blue). Coloured dots indicate the position along the ridge where the deflection envelope is maximum for the frequency coding by colour. X, apex of the TR; Y, base of the TR.