Meaning: This means that the room is very quiet and there is no noise.
Choice of Words: The word "filled" means that something is completely occupied or covered by something else. In this case, the room is filled with silence, which means that there is no sound at all.
A hush fell over the room.
Meaning: This means that the room suddenly became very quiet.
Choice of Words: The word "hush" means to become quiet or silent. In this case, a hush fell over the room, which means that the room suddenly became very quiet.