Hard of Hearing Character in the movie 'Knowing'

In 1959, as part of the dedication ceremony for a new elementary school, a group of students is asked to draw pictures to be stored in a time capsule. But one mysterious girl fills her sheet of paper with rows of apparently random numbers instead. Fifty years later, a new generation of students examines the capsules contents and the girls cryptic message ends up in the hands of young Caleb Koestler. But it is Calebs father, professor John Koestler (Nicolas Cage), who makes the startling discovery that the encoded message predicts with pinpoint accuracy the dates, death tolls and coordinates of every major disaster of the past 50 years. As John further unravels the documents chilling secrets, he realizes the document foretells three additional events the last of which hints at destruction on a global scale and seems to somehow involve John and his son.

Caleb Koestler is hard of hearing and wears a hearing aid. Viewers are told that "sounds get all mixed up for him but the hearing aid helps" and that he is "fluent in sign language". Throughout the movie, the father and son sign that they will be "together forever".
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