This is a very good question. What noise IS Laertes responding to? What is happening outside? Is Ophelia making crazy noises? Is someone fighting her? Is there someone who is preventing her from coming in loudly?
The Danes are clearly advocating for her entrance but she’s not in yet. Is she singing already? Are others trying to shush her? These are the questions that a lot of productions fail to ask and then end up bloodless and dry.
This is a good question. A good production will have a good answer.