Ambisonic sounds

Note: You can hear our ambisonic demo by checking out the experience, Ambisonic Audio Demo!, in Sansar. Make sure to wear headphones and turn around as the sound plays.

Sansar supports ambisonic surround sounds in AmbiX (ACN-SN3D) format, which is quickly growing in popularity and supported in other VR and 360-degree environments like Google's Jump and YouTube. Ambisonics have been around for decades, and there has been revitalized interest due to their usefulness in virtual reality.

A supported ambisonic file contains four channels of audio which sum to a spherical whole, and are spatialized accordingly in a scene. There are many variations out there; you may see reference to various "formats" and "orders". For the sake of simplicity, we use what's sometimes referred to as "first-order, B-format" AmbiX.

Note: The ACN channel order is different than some other B-format signals like FuMa. If you're trying to upload a (likely older) ambisonic file into Sansar and it results in an error, it's in the wrong format with a different channel order. You'll need a converter to make those Sansar-ready.

You can easily upload an ambisonic .wav file into Sansar, and use it to populate a scene with 360-degree surround sound:

  1. Rename the file extension from ".wav" to ".ambix" for it to be recognized.
  2. Follow the same uploading a sound steps used for regular .wav files.
     upload_ambix.png
Tip: if you need to batch-rename many files, get a utility like Renamer to save time.


Getting the most out of ambisonics

Ambisonics are decoded in Sansar so they can be enjoyed binaurally, with a quality pair of headphones like the built-in ones on the Oculus Rift. As you turn your head around — and this is especially noticeable in VR mode — you'll hear the ambisonic soundfield also rotate relative to your viewing/camera position. You don't need to manually position elements, and it can provide a convincing 3D illusion and supplement existing mono/stereo sound emitters in your scene.

Like mono/stereo sounds, ambisonics can be used as in-scene emitters with falloff, or as Scene SettingsSOUND SETTINGS > Ambient Sound. Note that since ambient sound plays continuously at the same volume no matter what your camera position is and can't be rotated, it may sound unnatural as you walk around and isn't the intended use of a sound that belongs spatially in the scene. And also like stereo sounds, rotating an ambisonic emitter reorients its soundfield.

Known issue: Ambisonic rotation is currently broken. A fix will be in an upcoming release.

Another advantage of ambisonics is that synchronous sight and sound can provide an enhanced sense of immersion. For example, if you've scanned a real-world environment using a 360 camera like a Matterport Pro 3D, and you want the actual on-location sound to match. You'd set up ambisonic-supported microphones at the same location to record the "sonic fingerprint" of that place, then upload both the visual meshes and ambisonic soundfield into Sansar. Aligned correctly, it could feel a lot like being there!

Like any tool, ambisonics is not a one-size-fits-all for sound needs. Knowing when to use it is key:

  • More channels means more complexity, and since the file is "baked" or "flattened" as-is, it can be quite difficult — if not entirely impractical — to remove unwanted soundsources. For example, if you recorded a babbling brook and birdsong in the wild — but a loud train suddenly passes by in the distance — even with advanced noise manipulation tools, it could be incredibly difficult to "clean up" the train noise. It'd probably be better to make another recording (and monitor it carefully).
  • For the same reasons, if you want flexibility with positioning specific sounds to match in-scene objects as you iterate creating an experience, mono/stereo sounds may be a more appropriate choice. It's easier to move objects to correspond to cues in an ambisonic soundfield than vice-versa.
      

Ambisonic resources

We recommend reading Creative Field Recording's comprehensive guide to learn more about the intricacies of ambisonics, insights from veteran sound designers, and how to make your own recordings. If you feel adventurous, you can get started by buying a Zoom H2n for about US$150 new. Feel free to share and sell your field recordings on the Sansar Store!

If you'd rather not author your own ambisonics, you can download ambisonic files for testing and use in your scenes from these sources. Be sure to read any applicable licensing terms, and remember to rename their suffixes to .ambix before uploading:

There are also various high-quality sound stores that sell ambisonic sounds. Before buying, make sure they're in the correct format and loop seamlessly (if needed). For example:

As with visual VR, there's a lot of experimentation happening in this area, so expect the selection and quality to keep growing. Happy ambisonic explorations! 

 

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