Today, Valve has introduced the Steam Audio SDK to the public, which will allow developers to create a deeper experience and quality with sound and acoustic. This spatial audio plugin is designed to deliver “An advanced spatial audio solution for games and VR apps.”
Steam Audio adds physics-based sound propagation on top of HRTF-based binaural audio, for increased immersion. Sounds interact with and bounce off of the actual scene geometry, so they feel like they are actually in the scene, and give players more information about the scene they are in.
Valve is using some of the 3D audio technology from impulsonic, a company they acquired this past January. What makes Steam Audio special is that it uses HRTF-based binaural rendering. HRTF allows a way of recreating how a sound is affected by a listerner’s head, ears, and torso, which results in subtle cues to pinpoint where the sound is coming from. HRTF-based binaural rendering also has a very low CPU overhead where you can hurdle thousands of sources using a single CPU core. In addition, this technology minimizes the frequency coloration of audio clips, while maintaining good localization.
Steam Audio will also simulate how objects occlude sound sources. On top of the raycast occlusion that a lot of game engines support today, Steam Audio will also support partial occlusion. This means that when a partial sound source is recognized, Steam Audio will only partly occlude that sound. Steam Audio will include technology where you won’t need to create special occlusion geometry just for sounds. Instead Steam Audio will use your existing scene geometry to occlude sounds.
For physics-based reverb, Steam Audio uses the actual scene geometry to simulate it. If for instance you are around a bend, you can hear the reverb in a realistic geometric sense where sound bounces off objects and walls. This lets users sense the scene around them through subtle sound cues. An amazing thing about this physics-based reverb is that it’ll take into account the material properties. Sound will resonate different from objects such as carpet versus a metal wall.
The new audio plugin will also simulate sound propagation in real time. This will save developers a lot of time where developers had to model sound effects manually and approximate sound propagation using hand-tuned filters and scripts.
Another amazing component to Steam Audio is how it’ll be able to bake sound propagation and reverb effects in a static scene. If for instance your geometry is mostly static, you’ll be able to bake reverb during design. If a sound source is fixed at a certain place, you’ll be able to bake sound propagation effects during the design phase. This is important for VR experiences as it’ll help with audio positioning during design.
“With Steam Audio, sound appears to flow and wrap its way around mazes and corridors accurately, and adapts to changes in geometry and materials on the fly,” said Emily Ridgway, an employee at Valve.
Steam Audio SDK is currently for free on PC Mac OS, Steam OS Linux, and Android platforms. The audio plugin is integrated with Unity and C API that you can download today. Unreal Engine 4 compatibilities are coming soon according to Valve. This is great news for developers as it’ll help create a deeper, more immersive experience in VR.