Fig. 14

Waveforms and spectrograms (re 20 \(\mu\text{Pa}^2\)) of airwaves excited at varying levels. \(V = 5\) \(\text{ cm}^3\) bubble bursts in a suspension of \(\phi = 0.4\). Air column lengths L (cm) are annotated (see Additional file 6: Movie 6 and the Graphical Abstract for the images of (e)). Waveforms are detrended and highpass filtered at 500 Hz. Running windows and overlaps are (a-d) 4.096 ms and 4.000 ms, (e-f) 8.192 ms and 8.100 ms, respectively. Blue \(\bigtriangleup\) and \(\bigtriangledown\) indicate the \(f_{\mathrm{A}}\) (\(n = 0, 1\), respectively) calculated from Eq. (20). Pink \(\triangleright\) and \(\triangleleft\) indicate the \(f_{\mathrm{H}}\) calculated from Eq. (11) using aperture radii \(R_{\mathrm{a}}\) measured at the times indicated on the time axis. In (f), \(f_{\mathrm{H}}\) is not calculated because the timing of the aperture opening could not be determined from the images