From the series "Soundwaves: The Symphony of Physics", this clip has the physicist Helen Czerski running a plate and asking a well-posed question: is there a way to visualise the sound frequencies an object has? The phrasing matters. The figures belong to the plate, and the tone simply selects which of the plate's own patterns you see.
Czerski is good on why that is interesting beyond the aesthetics. Every object has a set of frequencies it prefers to vibrate at, and making them visible is the beginning of a general technique — it is why engineers do modal analysis on turbine blades and violin makers tap plates.
Broadcast production values mean the sand reads cleanly and the camera angles actually show the nodal lines, which is not guaranteed. At five minutes it is the best television treatment of the subject currently on YouTube.