Here's the same field with just dots, more closely spaced

Heard that arbitrary gifs could now be posted, so here's an acoustic dipole with path-lines

But in the subsonic, evanescent case they follow elliptical paths, isn't that cool?

These are fairly standard animations, but what I worked out how to do today, and am feeling unbearably smug about, is to include the path-lines followed by the fluid elements as they vibrate. For the supersonic case they just move back and forth in the direction of propagation

What if the bending wave travels subsonically? Then there's nothing left for a horizontal wavelength and instead the amplitude rapidly diminishes with distance from the wall - the jargon is that it evanesces in that direction

Before I switch to the new preferred colourmap, here's a couple of animations I made for a short course I'm teaching on that use bwr for consistency with the rest of the slides (sorry).

So, I present a solution of the 'wavy wall' problem in acoustics

Up against it, under the same conditions is SBVe, where the negative pressure is represented by sky-blue rather than regular blue

Thanks for all your comments, here and elsewhere. BuVe (blue-white-vermillion) seems to be the winner on accessibility so far, so it goes through to the next round, in which the dots are suppressed

And SBOr, ibid

BuVe from the same set (which is based on the Okade & Ito colour-set)

Late entry: BurP from Nathan Sanders CBcm

Lastly, for now, here's broc from the same collection

And here's vik from F Crameri's scientific-colour-maps

Next is the shifted version of the twilight map, which is grey, rather than white at the centre

Here's pyplot's seismic, which is more intense but I'm not sure that makes it more accessible

Testing colour-maps for acoustic-wave visualisations; grateful for any feedback anyone has

First up is pyplot's bwr, which I've been using so far, but isn't great