Why is the constant mention of ears in Shakespeare's Hamlet significant?
In Shakespeare's play, Hamlet, the ear is an important image for several reasons.
First, it was publicly announced that Hamlet's father died from being bitten by a snake while he napped one day in the garden, however, it was from poison poured into his ear by Claudius.
Sleeping within my orchard, / My custom always of the afternoon, / Upon my secure hour thy uncle stole / With juice of cursed hebenon in a vial, / And in the porches of my ears did pour / The leperous distilment... (I, v, 64-69)
Before Laertes leaves for school, he warns Ophelia not to pay too much attention to what Hamlet has to say to her; if Hamlet says he loves her, she should not listen.
The sense of hearing is especially important regarding Polonius. The old man is forever hovering closeby, trying to hear conversations in which Hamlet is involved to glean information for Claudius—whether it is between Ophelia and the prince, or Hamlet and his mother. It is Polonius' penchant for spying in this way that leads to his death. And it is Hamlet—hearing Polonius hiding behind the arras (curtain)—that springs to action. As Gertrude calls out for help, believing Hamlet means to harm her, the concealed Polonius hollers for help, and Hamlet (mistaking the hidden man for Claudius) triumphantly shouts:
"How now? A rat? Dead, for a ducat, dead!" (III, iv, 23)
...and mistakenly stabs Polonius through the fabric of the wall hanging.
Lies are delivered in several instances; for instance, Claudius poison's Laertes' mind against Hamlet so as to manipulate Ophelia's brother into plotting to murder Hamlet in a "sporting" sword fight. It is Laertes' willingness to listen to Claudius' lies that leads to his death.
The ear played an important part in delivering almost every character in Hamlet to his or her death by the play's end.