While describing his beloved Ligeia near the beginning of the short story of the same name, the narrator waxes poetic about his time spent interacting with her prior to her death. In doing so, he uses a simile comparing her to a shadow and metaphorically suggests that she is made of "marble":
I would in vain attempt to portray the majesty, the quiet ease, of her demeanor, or the incomprehensible lightness and elasticity of her footfall. She came and departed as a shadow. I was never made aware of her entrance into my closed study save by the dear music of her low sweet voice, as she placed her marble hand upon my shoulder. [...] It was the radiance of an opium dream—an airy and spirit-lifting vision more wildly divine than the phantasies which hovered about the slumbering souls of the daughters of Delos.
In the quote above, Ligeia is described as a “shadow,” as “marble,” and as having the “radiance of an opium dream”—in other words, in her death she has been transformed from a flesh-and-blood lover to an idea on a pedestal, an otherworldly entity. The narrator’s extreme devotion to this idealized figure, at the expense of remembering her humanity, is the first of many signs of his increasing madness.
The simile the narrator draws in “The Tell-Tale Heart” between the old man’s eye and that of a vulture’s serves to emphasize the narrator’s own madness:
I think it was his eye! yes, it was this! One of his eyes resembled that of a vulture—a pale blue eye, with a film over it. Whenever it fell upon me, my blood ran cold; and so by degrees—very gradually—I made up my mind to take the life of the old man, and thus rid myself of the eye forever.
The extreme chilling effect that this pale blue eye has upon the narrator is bizarre and unprompted, and this simile therefore reflects the narrator’s unreliable logic. Besides this description of his eye, the old man is given little else in the way of characterization—save for a few key details: he never wronged or insulted the narrator, and the narrator loved him. The vulture comparison made by the narrator stands directly in opposition to these two facts. This begs the question of whether the narrator is being truthful with himself and the reader regarding his feelings towards the old man and towards his own actions. By comparing the old man to a predatory bird of prey, he dehumanizes him, subtly trying to justify his actions even as he attempts to disprove accusations of madness.
“The Tell-Tale Heart” is full of auditory imagery. Sound—imagined and real—plays a large role in translating the paranoia of the narrator to the reader. Take the passage below, for example:
And now have I not told you that what you mistake for madness is but over acuteness of the senses?—now, I say, there came to my ears a low, dull, quick sound, such as a watch makes when enveloped in cotton. I knew that sound well, too. It was the beating of the old man’s heart. It increased my fury, as the beating of a drum stimulates the soldier into courage.
The beating of the old man’s heart while he is still alive stimulates the narrator to action, prompting him to end the man’s life as he had been planning to for the past eight days. Whether the narrator has supreme hearing or the heartbeat was merely a product of his imagination, the language he uses to describe the sound is noteworthy. The noise begins as a soft, muted sound but quickly grows, taking on the quality of a drum and therefore turning the narrator himself into an almost heroic figure for the act of silencing it. The narrator’s figurative comparison of his actions to that of a soldier's courage demonstrates his distorted view of himself.
Later, the narrator’s hallucination of an echo of this same sound drives him to confess his own misdeeds to the authorities:
Yet the sound increased—and what could I do? It was a low, dull, quick sound—much such a sound as a watch makes when enveloped in cotton. I gasped for breath—and yet the officers heard it not. I talked more quickly—more vehemently; but the noise steadily increased.
Thus, in the passage above, the steady drum beat which at first allowed the narrator to exercise his strength and power, and feel in control, becomes an ever-increasing signal of his own guilt. Sound transforms the narrative, allowing the reader an inside peek into the unreliable narrator’s inner psychology.