Why a diagram cannot be spoken and figures vanish on contact

Some material is not difficult in audio, it is impossible.

A diagram is a claim about relationships held in view together: this sits inside that, these two connect, that one is off to the side. Reading it aloud converts a simultaneous structure into a queue, and the listener has to rebuild the whole thing in working memory from parts delivered one at a time while new parts keep coming. Almost nobody manages it. What arrives is not a partial diagram, which would still be useful, but an impression that something structured was described and could not be caught.

Numbers fail even faster, and for a slightly different reason. A figure heard once has no anchor. There is nothing to look back at, nothing to compare it against except another figure that has also already gone, and no way to hold a sequence of them without deliberately memorising as you listen, which is not listening. A spoken series of values is functionally silence with tone. The listener retains the shape of the claim (things went up, one option cost more) and loses every quantity that made the claim specific.

The honest response is not to speak such material more slowly or more clearly. It is to change what the spoken version is for. Audio can carry the meaning of a structure: why it is arranged that way, what surprised somebody about it, what follows from it. It cannot carry the structure itself. Say what the picture means and point to where the picture is. That division of labour is not a compromise. It is each medium doing the part it can actually do.