Zooey's voice breaking that dial tone in the beginning in his phone call, and then the resumption of it afterwards, that dial tone encases Zooey's voice, so that what Zooey says to her is one of the rays of light of God's creation, one of those things, like Shakespeare, that is part of the whole created world, but what Franny can tune into, after hearing his voice, is that very essential divine sound, meaningless sound. 