simile/metaphor
In looking at this line, what we see is that the author is comparing the whip’s movement and sound to that of a piece of wood being shattered by manner of splintering. The author is doing this so that readers, who may not have had any experience of seeing a ringmaster at a circus crack a whip, may have a good idea as to just how the whip may have sounded. This is a common technique in literature and poetry called simile/metaphor. Technically, the air cannot be actually be splintered, thus, we know that this is figurative.