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Valve today announced the Steam Audio SDK, a spatial audio plugin that the company says is made is designed to “enhance all interactive products, specifically VR applications.” The company has launched a beta of the SDK today supporting Unity, and support for Unreal Engine is on the way.

Realistic sound is an important but often underappreciated aspect of the immersion equation in VR. Basic stereo output works well enough for gaming on monitors, where the world is abstracted away from an immersive first-person view. But when your eyes are convinced they’re inside the game thanks to VR, your brains has certain expectations for how the world around you should sound. Our brain literally uses audio cues to understand spatial information, especially about what’s not currently in our line-of-site.

VR audio isn’t a ‘solved’ problem, but some of the solutions available today make a huge difference. And now, developers wanting to implement spatial audio in their VR apps have a free option, thanks to Valve’s newly announced Steam Audio SDK. Available now with support for Unity, the Steam Audio SDK will also soon support Unreal Engine. The company says that use of the spatial audio tool is completely open and supports Windows, Linux, MacOS, and Android, and is not restricted to any particular VR device or to Steam, which means developers building VR apps for the Oculus Rift or Gear VR, for instance, are welcome to use the tool. The SDK also currently includes a C API for integration into other game engines and middleware.

The technology powering the Steam Audio SDK is a continuation of the work of Impulsonic, who developed the Phonon audio tools, which has been acquired by Valve.

“Steam Audio is an advanced spatial audio solution that uses physics-based sound propagation in addition to HRTF-based binaural audio for increased immersion,” Valve wrote in a statement issued to Road to VR. “Spatial audio significantly improves immersion in VR; adding physics-based sound propagation further improves the experience by consistently recreating how sound interacts with the virtual environment.”

Historically, realistic physics-based sound calculations have been computationally restrictive, especially for real-time applications, and efforts to simplify some of the underlying physics surrounding sound wave interaction with 3D geometry have results in decent, but not perfect spatial audio. With the rise of VR, more interest has been given to this area, and companies like NVIDIA and others have taken a stab at the problem.

According to Valve, one of the biggest benefits of the Steam Audio SDK is automatic real-time sound propagation:

In reality, sound is emitted from a source, after which it bounces around through the environment, interacting with and reflecting off of various objects before it reaches the listener. Developers have wanted to model this effect, and tend to manually (and painstakingly!) approximate sound propagation using hand-tuned filters and scripts. Steam Audio automatically models these sound propagation effects.

You can find more details on the features supported by the Steam Audio SDK here.