Sound Volume not Updating

[tyuah8]

Once a sound starts playing at a location on the map, its volume will not update when the screen is moved towards or away from the location.

To reproduce, perform the following:

    1. Let the enemy AI build a Nuclear Missile Silo.
    2. Right before the missile is fired at your base, move the screen to a
       location far from your base.
    3. Let the enemy AI fire the missile at your base.
        - Notice that the Nuke Siren sound is very quiet, because the screen is
          far from the point of impact.
    4. Move the screen to your base.
        - Notice that the Nuke Siren sound remains quiet even though the screen
          is at the point of impact.

The correct behaviour is that the sound volume will automatically increase/decrease as needed based on where the screen is located on the map. This is also the same behaviour as the original game.