I think that the element of silence plays a role in two main settings. The first would be the shooting of Candy's dog. There is a silence between the moment the dog is led outside of the living quarters until the point it is killed. This silence is one that can represent a great many things, such as Candy's own guilt at allowing the cruelty to happen. It can also represent the death of hope. To a large extent, Steinbeck seems to indicate that there is a "sound" associated with the activity that allows hope to happen. For George, it is the sound of the dream of owning his own farm. For Lennie, it is the sound of animals. This silence is something that is antithetical to such hope because of its implication of a lack of activity, a lack of connection to one's vision of the future. In the instances where one does not hear that sound, silence seems to indicate a lack of hope. In the shooting of Candy's dog, one hears this. At the same time, when Crooks' life is described, this similar silence is present. Crooks' world is a silent one because of the lack of connection to others. This silence seems to indicate the lack of hope that he experiences because of this isolation. It is why that the silence accompanies Steinbeck's description of Crooks' setting in chapter four in the beginning and end, indications of Crooks' life both before and after people enter it.