Lately I’ve been researching into the subject of audio occlusion, something that we take for granted pretty much all the time in the real world. In ‘DATA Labs’ there were a few instances in which I noticed issues with this, in particular with the sound of props from other rooms being clearly audible in adjacent rooms, even with walls in between – not very realistic!
I know there are a few ways to go about this, an especially easy option is to use Unreal Engine’s built in audio occlusion features, but in this instance I chose to use Snapshots in FMOD to achieve a similar result. I’m going to develop these over time but for now here is a quick run down of what I’ve done so far.
Hopefully you’ll be able to hear the effect of this above – as I move between different rooms the balance of levels subtly changes – in the break room for example the coffee machine sound replaces that of the main hum and air conditioning of the office environment. In the rear office, a similar snapshot ducks the levels from the main office creating a more foreboding and eerie atmosphere.
Above you can see a top down of the level showing the main rooms / areas. Each of these has a mixer state associated with it, or in FMOD speak – a ‘Snapshot’. Each snapshot can control pretty much whatever you want, however in this case I’m using them to control levels of certain props, reverbs and low pass filters.
The picture above shows the snapshot for the break room – the controls that are visible are included in the snapshot, and as you can see the level of the computer group to the left is fairly low, the environment group has also been lowered a little but the rest left untouched (dotted lines). I also added a low-pass filter to ease off the higher frequencies from the sounds of these groups, much in the way that the built in occlusion works in Unreal. I then simply created a trigger volume to trigger this event when you enter the break room.
Another thing that I find helps with snapshots is allowing them to fade in and out using the built in intensity parameter. This helps to create smooth changes between mix levels that might otherwise ruin the immersion for the player.
I’ll be continuing to develop this system over time, and I’ll probably look at the built in system in Unreal as well which I feel might offer some benefits in this area. If anyone has any tips or suggestions for audio occlusion using FMOD I’d love to hear them!