The soundscape area is meant to be a sort of one-in-all solution to set up much of the needed background sound data. It can set reverb, play ambient track, change volume on sounds and turn on/off sound entities. Make sure you know how the areas work before start placing sounds in a level.
Reverb is pretty basic and just do what the settings say. If there are many reverb areas that overlap then the one with the highest prio will be used. However, note that if Reverb is not active for an area, then it will not be taken into account at all, no matter what the prio is set to. So if you want an area that turns off reverb, then it needs to have reverb active and type set to "off".
The soundscape area can start sounds as the player's head enters the area. There are two types of these Sound entities and Background sounds.
The sound entities are sounds that are already placed in the level and they will be either started/stopped when the player is in or out of the area. If two areas over lap and are of the same level then the one with the highest prio will be used. This means that if the areas have different levels, then sound entities from many areas can be played (or not played) at the same time.
Background sound is just a 2D sound that is started when an area is entered. Prio is used to determine what sound to use if many of the same level overlap. However, if many of different level overlap, then the behavior gets very interesting. What happens then is that the background sounds from lowered numbered levels will get lowered according to the ParentVolMul setting in the higher numbered ones. This is meant to simulate the background noise getting lowered as you step inside a house or similar. For instance, if the player is inside one Global (0) area and one Room (2) area, then the background sound will from the Global one will be lowered according to ParentVolMul in the Room one. This multiplying is applied all through the hierarchy, so if the player is inside areas from levels 0 -> 3, then any sound in level 0 will be multiplied by the setting in 1,2 and 3 all taken together.
This can be really used for whatever and is currently used for playing different kinds of footsteps. It applies an extra parent folder to the footstep to be played if the variable is not empty. It can also be used by script function Sound_CreateAtEntity_UsePrefix to easily play different sounds depending on which soundscape area the player currently is in.
Use copies of an area to cover complex shapes
The soundscape areas are built to behave nicely when many soundscapes with the same properties overlap. It is often a hassle to fill certain rooms with areas without going out of bounds. With Soundscape areas this is easy as the game will treat overlapping areas with the same properties as essentially the same area. So there is no start/stopping going on when going between areas that have the same sound names, etc