The Distinction between Surround, Spatial and Volumetric Sound
This article was inspired by a question we got from Peter Moore, at FTL Labs. He asked:
“Why are people recording spatial sound in 8 channels when Dolby Digital only supports 7 full range channels? ie why / how is VR inadequate with 7 channels?
Isn’t the market for spatial sound movie soundtracks much larger than VR? If so I don’t get why spatial sound isn’t sticking with the 7ch Dolby Digital standard / mic spacing?”
I thought Peter’s questions are great because they point out the terminology salad we currently have in our newborn medium. Therefore, I wanted to use this opportunity and clarify some terminology that may be confusing.
spatial sound and surround sound
7ch Dolby Digital is Surround sound format, meaning it’s for 2D cinema. Surround sound is what you hear when you go to the movies. It’s similar since it’s audio all around the viewer, but the key difference between surround sound and spatial sound is that spatial sound is reactive to the movement of the player in VR. It’s within the way the output file is being encoded so the VR video player can locate the sound in space and react to the viewer’s movement. This encode adds HRTF (head-related transfer function) data into the format. Surround sound does not have that movement capability, it just plays the 5 or 7 channels around the viewer.
you CAN record sound on surround sound format (with 5.1 or more channels), like with the Zoom H3-VR: 5.1 Surround Sound and implement it in your spatial mix, but you would have to export and encode it on a spatial sound format for distribution (ambisonic format for example, using FB360 Encoder to encode). The Zoom H3-VR for example has an internal system to convert the 5.1 recording into an ambisonic A-format for distribution on implementing it in a spatial sound mix with the Facebook 360 Workstation for example. (although it is not required to convert the 5.1 recording to ambisonic in order to implement it in a spatial mix. You can just chose 5.1 channels in the input setting in FB360 workstation while mixing)
Another confusing point that is important to mention. There is no need for special headphones in order to enjoy spatial sound. You can play 360 videos with spatial sound with regular headphones from any VR supported phone or headset. The movement of the phone or headset displays the sound into your headphones based on the direction you are looking at.
So to summarize, spatial sound is for VR and surround sound for cinema. You CAN record with surround recorders and use FB360 or Hear360 plugins to design the recording spatially and encode it for spatial sound.
Walking forward, walking back
Peter also asked about “walking forward” or “walking back”, which is important to differentiate as well that these aren’t capabilities within spatial sound. Spatial sound is for 360 video, therefore it’s stationary. You can’t walk, you can only turn.
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For walking in the space it’s for VR video games (which is programming sound in a game engine like unity. We touch on it on the course but it’s more a video games field. Not 360 cinema). Videos that you can walk around the space are called volumetric. And the tech in video volumetric is still very very new and expensive, and kind of not “production ready” yet. Let alone the sound in the space.
So to summarize, spatial sound is for VR and surround sound for cinema. You CAN record with surround recorders and use FB360 or Hear360 plugins to design the recording spatially and encode it for spatial sound.
Surround vs Surround vs Volumetric
So again, to summarize, spatial sound is stationary for 360 video and surround sound is for cinema. Walking around in the space in VR is mainly found in video games at the current stage of the tech and implementing sound within volumetric is being done on a game engine, it is not spatial sound. We CAN record sound on a surround sound format (or any format really) and implement it in a spatial sound mix.
I hope this help to clarify some terminology. If you would like to dive deeper into the field and enjoy demonstrations, work methods and detailed examples for how to work with spatial sound, please consider purchasing our full spatial sound course and get all you need to work in the field become a real pro.
This article was written by Nir Netzer. Nir is a VR director located in Los Angeles. He directed 360 content for DreamworksTV and Oculus Launchpad and he is VRTL’s instructor for the spatial sound course. To learn more about Nir’s work you check out this site: http://www.netzerland.com
