Fig. 11

Single close-up video recording of one Asian elephant showing pronounced vibrations associated with vocalization. a Image from video recording by CAM 4. Image probes for vibration analysis are indicated on the image. b, c Vertical (b, yellow line in a) and flipped horizontal (c, green line in a) scan lines plots over time. The duration of one vocalization event (event 28 in Fig. 9) is highlighted by dashed lines. d Audio spectrogram. e–i Analysis of vibrations at different body positions during the video capture. Plots of normalized pixel intensity over time at the frontal head (e), throat (g), and posterior (i). f, h Vibration spectrograms from frontal head and throat signal. By performing a short-time Fourier transform (6-bit window) of the frontal head and throat signal, vibration spectrograms were generated (f and h) showing a good match with audio spectrogram (d)