Ambiences

Going into this project it was clear that, this being a stealth game, ambiences would play a particularly important part in creating and maintaining an appropriately suspenseful mood. Due to the historical milieu of the game, it was also going to be important to create a very natural soundscape, which would mean, in part, employing a lot of subtle variation.

As with many games, the ambiences for Children of Liberty are made up of two components - longer continuous sounds (in the walk-thru of the Warehouse level, these are the wind and ocean), and shorter 'stingers' (the gulls, shutters, crashing waves, dock sounds and creaks of the Warehouse level). However, since I was designing and building the audio engine from scratch, I wanted to figure out how to bring the most variation and randomness into the soundscape as possible, in order to increase realism, while also addressing technical considerations such as hard disk space, runtime memory and streaming needs.

These practical and creative considerations led to the following approach:

1. Continuous ambience files were kept small by breaking larger files into smaller segments.
2. This allowed the limited streaming resources available to be reserved for music, which requires the largest files.
3. By playing these segmented ambience files in random order, more variety is created than would be achieved by playing a single, longer loop repetitively, addressing both the need to keep these non-streaming resource files small and the desire to maximize variation.
4. The software object that randomly selects the next clip to be played also creates a cross-fade across the change from the preceding clip. The timing and placement of the cross-fade is randomized, within configurable parameters, creating yet more variation. An added benefit of this cross-fading of segmented files is that audio loops with perfectly matched start and end points are not needed.
5. Different components of the continuous ambiences (the ocean and wind) are kept as separate layers, which allows them to be re-used individually or at different relative volumes in other levels, such as Long Wharf, which follows the Warehouse and takes place outside on the docks where the ocean would be comparatively louder. This also creates greater variety than one combined layer because of the randomness in the juxtaposition that occurs between the layers.
6. The short stingers are also assigned to separate layers, allowing them to be re-used individually, and to create more variation in their relative timings. Each stinger layer may have different time interval triggers - by having some sounds triggered only at very long intervals for instance, you get an occasional unexpected surprise.