TELL-TALE heart what does the narrator hear at the end of the story that causes him to confess to the murder

Answer The heart of the dead body he killed

Explanation:

It is hearing the "tell-tale heart" because of his acute hearing that forces the narrator to confess his deed as he remains unable to ignore the loudening sound of his own guilt and crime. Perhaps we can infer that what he is symbolically hearing is his own conscience, forcing him to face the consequences of his actions, as it is only the narrator that hears this sound. Either way, it is this sound that forces him to confess, shouting, "It is the beating of his hideous heart!"