Brian’s hearing became more acute the longer he was in the wilderness.
Not long after Brian crashed in the wilderness, he began to realize that his sense of hearing was becoming more acute. With practice, and the fact that things were so much quieter, he was starting to hear things he had never heard before in civilization.
Since the plane was small and the pilot died of a heart attack in the plane crash, Brian was all alone in the wilderness. By himself, he had to rely on honing his wits to survive. This meant improving whatever survival skills he had.
I am not the same, he thought. I see, I hear differently. He did not know when the change started, but it was there; when a sound came to him now he didn't just hear it but would know the sound. (Ch. 11)
Brian realizes that since he has developed his hunting and survival skills, he knows where a sound is and what it is almost as soon as he hears it. He can tell what something is without seeing it. He knows if it is food or a predator. He knows if it is a danger to him or a blessing. Brian makes a note of the fact that he did not have these skills before. None of it used to be in him, but “now it was a part of him” (Ch. 11). Now Brian has learned how to make a shelter, keep a fire, and feed himself. He can survive on his own without any adults, and is doing quite well.
Brian’s recognition of his acute sense of hearing, and the change in his sense of hearing, demonstrates that he is aware that this experience has changed him. He has spent so much time trying to survive that the change in him came as a sort of shock. He didn’t realize how different a person he became.
I agree with university-of-answers post; vague questions get vague answers. When asking a question, there needs to be more detail given for someone that is outside the classroom. There needs to be a section, chapter, or instance that another reader can locate to begin searching for the answer.
Im not quite sure what you mean by "What happened to Brian's hearing in Hatchet."
However, if you are referring to win the plane crashes and Brian is dazed from impact, than it is because he is still recovering from the impact.
If you can provide more information i would love to expand on my answer