Commercial wave drivers are expensive, which is why school physics departments often skip this demonstration. Yeany's route around it is a free online tone generator, a discarded amplifier, a driver built from an old speaker and plates cut from sheet metal. He is candid that the plates were cut quickly, are not square, and the centre holes are not exactly centred — and they work anyway.
That candour is the point. The failure modes people fear when building a plate — imperfect geometry, a scavenged driver, an amplifier of unknown provenance — turn out to matter much less than expected. The nodal lines still appear cleanly.
Six minutes, filmed with almost no production, from a long-running channel of classroom physics apparatus. Pair it with his laser-and-bucket sound visualiser for a fuller picture of what scrap parts can do.