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.

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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.