Why was the story of Ethelred a fitting one for the narrator to read given what noises he actually started hearing?

The story of Ethelred, who is tormented by a faint sound that eventually drives him to madness, parallels the narrator's experience of hearing a faint ticking that eventually becomes unbearable in "The Tell-Tale Heart." Both stories involve the theme of an amplified obsession that leads to a psychological breakdown, making it a fitting choice for the narrator to read given his own escalating torment over the old man's eye.