Four short lines, and they turn the ear into something almost human. The speaker imagines how much an ear must suffer out in the world, always open, always taking in whatever comes, with no way to shut itself. The title, "Taken for granted," fits: we rely on hearing constantly and rarely think about what it costs.
Then the poem shifts to something more tender. The phrase "miracle of attendance to nobody" suggests that listening is wondrous even when no one is being listened to, or when no one notices the listening. The ear pays attention for its own sake. The last image, "a cave in the growing night," pictures the ear as a hollow, dark shelter as evening deepens, a place where sound echoes and is held.
The mood is quiet and sympathetic, a little lonely but also reverent. The speaker seems to feel both pity and admiration for this overlooked part of the body, and invites us to notice it too.