Final answer:
The sound that McMurphy makes as he assaults the nurse is loud and chaotic. This action makes the men question his sanity because it is a violent and aggressive act that goes against the norms of the institution.
Step-by-step explanation:
The sound that McMurphy makes as he begins to assault the nurse is not explicitly mentioned in the given passages. However, we can infer that there is a commotion and disturbance caused by the assault, as described by phrases such as 'The meeting of enemies, the sudden oath, the blows and fall' and 'A sudden chill ran through the room; the others stood transfixed'. These descriptions suggest that there is a loud and chaotic sound associated with the assault.
This action of assaulting the nurse makes the men question McMurphy's sanity because it is a violent and aggressive act that goes against the norms and rules of the institution. McMurphy's behavior goes beyond what is considered acceptable or rational, causing the other men to view him as mentally unstable or unpredictable. The violent act challenges the order and authority of the ward, leading to doubts and concerns about McMurphy's sanity.