In this quotation, where the narrator describes the horrifying sound of the cat's howling from within the tomb, Poe employs a literary device called imagery. Imagery is a verbal description of sensory information; the imagery can be visual (sight), auditory (sound), gustatory (taste), tactile (taste), or olfactory (smell). Here, the narrator uses auditory imagery in describing the sound when "the reverberation of [his] blows sunk into silence"—when he ceases the heavy rapping with his cane upon the wall, an action he performs with bravado, in order to prove his innocence and ease to the police who have come to investigate his wife's disappearance. We can imagine the stark silence following the blows with his cane upon the stonework, just prior to the horrific yowling of the angry cat. The two loud sounds interrupted by the silence seem to build tension.