Wave propagation on a tabla membrane

The video shows the propagation of the depression in the membrane after striking a /ɽ/ bol. For such a depression to travel across the syahi, the black central patch 8 cm in diameter, it took a time duration corresponding to ten frames. As the images were captured at 4000 frames per second, every frame corresponds to 0.25 ms.  Thus, 10 frames took 2.5 ms (10*0.25). Hence, the wave velocity on the membrane equals 32 m/s (8 cm/2.5 ms).