If you are not deaf in real life and dream that you are deaf, then it suggests that you are feeling secluded from the world. You may be closing yourself off from new experiences or shutting yourself out. Alternatively, the dream could indicate that your defenses are up. There is something that you are refusing to hear. Perhaps you have problems taking criticism. The dream could just mean that you are in need of some peace and quiet.
To dream that someone else is deaf suggests that someone close to you is withdrawn.