What does Jonas see and hear at the end of The Giver?
It is interesting that you select these two senses to focus on, as arguably a lot of what Jonas experiences at the end of this excellent novel is sensed intuitively than seen or heard. It almost seems as if the author is giving more importance to this intuitive sense than she gives to his physical senses, as we are told that Jonas felt himself losing consciousness as he descends on the sledge with Gabriel, and thus the perception of his physical senses is cast into doubt.
However, apart from this, we are told that as they descend, Jonas sees lights shining from rooms:
He knew they were shining through the windows of rooms, that they were the read, blue and yellow lights that twinkled from trees in places where families created and kept memories, where they celebrated love.
He also hears the sound of singing. However, note the way that in these descriptions the physical senses and what they perceive are intermingled with the intuitive senses, indicated by the words "He knew..." The author therefore deliberately creates a highly ambiguous ending where the majority of what Jonas perceives is not through his physical senses alone.