Overview

Background environment sound often consists of both ambient sound loops and random one-shots. Using the Entities AmbienceVolume and RandomSoundVolume attached to area shapes, one can create convincing environments.

Multi-channel looping sound events can be played as background ambient sounds in the levels. These are 3D sounds that reside within the confines of an area shape.

When the player enters the area shape, the ambient sound travels with the player, becoming, in effect, a surround sound. Once the player leaves that shape, the sound is left behind on the perimeter of the area shape.

An example of an ambience setup in a level.

Creating an Ambience Sound Event

Using the FMOD Designer tool, the sound event should have the following properties:

• It should be a 3D, looping event.
• It should have 2D speaker volumes set to emulate surround sound.

• It should have a parameter called spread.
• Two effects called 3D speaker spread and 3D Pan Level must be assigned to the spread parameter. They adjust how the sound behaves as you approach the area shape.

Basic ambiences are quite easy to place in a level:

• Under Objects/Sound, select AmbientVolume. Drag this entity to the level.
• Next, draw an area shape. Under entity links, click PickTarget. By selecting the AmbientVolume entity, it will be linked to that area shape.
• Whenever the player approaches or enters that area shape, the ambient sound will play.
• If you give the area shape a height, the area shape will limit the vertical dimensions of the AmbientVolume. If you leave the height undefined, the AmbientVolume will have an unlimited vertical dimension.

Properties of AmbientVolume Entities

Setting up overlapping ambient shapes

You might run into the problem that the outer most ambient volume will "bleed through" into your inner ambient shapes that you use for interior ambience.

Consider the following scenario:
You walk cross a jungle with constant birds singing, wind gusts, crickets etc. Then you enter a large bunker and walk deeper and deeper through a tunnel. The birds fade away and only a deep hollow tunnel ambience is audible. You then pass through a door into a control room with radio comms, radar beeps and tech ambience.

Problem:
On transitioning from the tunnel into the control room the outdoor jungle ambience will briefly play, its sound will "bleed through" from the outside.

There is multiple ways of preventing this behavior.

Double ambient shapes

• Each ambient shape setup consists of two shapes. Let's call them: A - the ambience shape itself (blue in the picture) and: B - the protector shape (purple)
• Both have to have a higher priority than the larger outdoor area. Both can have the same priority value. (e.g. 10 on the outdoor shape and 20 on ambience and arotector shapes)
• The ambience shape carries the sound that you want to hear and its properties are set accordingly to the indoor transitions and ignoring the outdoor sound
• The Protector Shape blocks the outdoor sound and therefore has to have all segments set to "obstructed", and has to be slightly larger than the ambience shape in order to encase it fully
• Exceptions on "Exit" segments: segments of Protector Shapes which represent the EXIT to the outdoor need to be set to "Not Obstructed". The Exit segments of an Ambience shape mustn't be surrounded by the protector shape. Here the ambience shape has to stick out of the Protector shape.

This option has the benefit of absolute and total control on the sound/level designer's part but creates more maintenance overhead in case of the level layout changing. You also do not need to create any flow graph and can do it within the level itself.

Disabling the outer ambience through flow graph

• You place a trigger (in this case a proximity trigger) between the two indoor shapes.
• Make sure to make it wide enough that the player cannot quickly move in between the shapes.
• Add a flow graph that simply switches off the outer ambience whenever you transition between the indoor ambience shapes.

This option has the benefit that you do not need to maintain a complex second shape, you can just modify the trigger when something changes. You need to make sure your flow graph is clean and keeps being maintained when things change as well though. If you use this method a lot you would be well advised to add a short (e.g. 500ms) fade in and fade out to your ambience sound events in FMOD to prevent any sudden silence (or crackling) from being heard when hitting the trigger.

Further Reading

• Advanced Features of Ambiences
• Area Shape and Box Sound Obstruction
• RandomSoundVolume Entities
• Using Reverb Volumes