Spatial Audio definition (vs. immersive sound and 3D sound)
Content
Spatial audio, immersive audio, 3D audio, surround sound. Four terms, used interchangeably by most people and by a fair amount of marketing. They do not mean the same thing, and the difference decides what you can actually deliver. This article sorts them out.
If you are looking for how spatial audio works rather than what the words mean, that is covered in how does spatial audio work.
I recently had the opportunity to dive deep into the topic with Thomas Riedel. Especially in the context of the Apple Vision Pro, his podcast is no longer called Metaverse Podcast, but Spatial Realities.
3D audio is slowly becoming mainstream. […] There was quite a lot of coverage, even in the Süddeutsche newspaper, where I was quoted in this article.
The four terms at a glance Why the word „immersive” carries more than music does is unpacked in immersive sound beyond 3D music.
| Term | What it actually says | What it does not say |
|---|---|---|
| Stereo | Two channels, left and right | Nothing about height or distance |
| Surround sound | Sound on one horizontal plane around you, 5.1 or 7.1 | Nothing above you |
| 3D audio | Height information is present, sound can sit above and below | Nothing about how you receive it |
| Spatial audio | The playback side: a position is rendered for your ears | Nothing about whether the content has real spatial data |
| Immersive audio | The experience of being inside the sound | Nothing technical at all |
The last row is the one that causes the most damage in briefings, and I will come back to it.
What is the difference between spatial audio and 3D audio?
3D audio describes the content: the material carries height information, so a sound can sit above or below you, not only left and right. Spatial audio describes the delivery: your device renders a position for your ears, usually with HRTF filtering over headphones.
That is why the two are not interchangeable. You can have spatial audio playback on material that has no spatial information in it at all, which is what happens whenever a device upmixes stereo. And you can have genuine 3D audio content that arrives as flat stereo because the playback chain never rendered it.
The evolution of 3D audio from surround sound
Media content must be available in specific surround formats such as 5.1 or 7.1 to work with those systems at all. The step to three dimensions is not more speakers, it is one extra axis:
“If you say you can move and hear the surround sound on one plane, front and back, the left ear and the right ear, then I would say Dolby Surround is two-dimensional. […] And only if I now start to be able to give height information to the object, then I would be in 3D in this area.”
Height information plus the consideration of head movements is what separates surround from 3D. Everything else is a channel count.
The 3D Audio Matrix clarifies
The definition of 3D audio depends heavily on the context in which it is used. It is a question I answer with my 3D Audio Matrix, a concept I developed to visualise the different aspects and applications. More about this on my blog and in my training course.
In the world of three-dimensional sound there is often a confusion of terms, which I address in the interview with Thomas Riedel:
“Many colleagues use Dolby Atmos and think they automatically create immersive audio. But many immersive media cannot be reproduced in the AC-4 format.”
What is the difference between spatial audio and immersive audio?
This is the pair that gets confused most often, and the answer is uncomfortable for a lot of marketing copy.
Immersive audio is an experience. It allows you to immerse yourself in the sound itself, far beyond the limits of technology. I have argued this at length in why immersive audio is more than 3D music. And that leads to the sentence I keep repeating:
“Immersive audio can also be stereo”
It emphasises that this type of experience is less about the number of channels or the complexity of the setup, and more about the feeling of immersion. A good song that gets you dancing in a club is as immersive as a complex multichannel system.
Spatial audio, by contrast, is a technical property. It says a position was rendered. It says nothing about whether anyone was moved.
That is why I find it critical when “immersive audio” is used as a synonym for “better”, to upgrade stereo and sell it at a higher price. You have to differentiate between immersive audio systems and platforms, meaning technologies, and immersive content and services, meaning experiences. What that content actually looks like across formats is collected in the 3D audio content overview.
What is immersive spatial sound then?
The combination is legitimate when both halves are true: spatial rendering that carries an experience. It becomes marketing noise when one half is missing. The practical test is simple. Ask what the content contains, not what the device supports.
What is the difference between spatial audio and surround sound?
Surround sound is speaker-bound and horizontal. The channels have fixed positions in a room, and you need the room to hear it as intended. Spatial audio is rendered for the listener, most often over two ears, and travels wherever the listener goes.
The practical consequence for a project: surround needs an installation, spatial audio needs a headphone. That single distinction decides more budgets than any format debate.
3D audio and the degrees of freedom
The true depth of 3D audio shows in the ability to move sound in all directions. In contrast to two-dimensional sound, where sound moves on one horizontal plane, 3D audio opens a world in which sound objects float vertically and envelop the listener.
“Only when I start to give height information to the object do we move into the realm of the three-dimensional. But even this kind of threedimensional sound is not enough.”
This is where degrees of freedom come in. If you rotate your head, that is dynamic head tracking, three degrees of rotational freedom. Apple’s headphones already do this, and the article on 3D audio headphones goes through the playback options.
With six degrees of freedom you are in gaming, XR, VR, AR and spatial computing. Movement in space does not work through Dolby Atmos but in game engines. The Apple Vision Pro audio features enable translation of audio objects too.
The full systematic breakdown of the degrees of freedom, with use cases per level, is in what is 3D audio and what are its benefits.
Why Apple made the confusion worse
Apple has genuinely understood spatial audio and pushed it. It has also teamed up with Dolby Atmos, and that combination causes a lot of the confusion.
“They have presented a lot of features of the glasses, but it feels like all their computers have additional speakers with spatial audio built in. But when is three-dimensional really three-dimensional?”
On the Apple homepage the term is “Spatial Audio”, while the German translation is “3D Audio”. The same product, two different words, in two markets:
“In German it’s ‘3D Audio’, and that suits us Germans who love numbers, data, facts”
Apple Spatial Audio is not really a term. For me it is an umbrella for headphones, computers and software from Apple that does something with 3D audio. What sits underneath it in practice is described in the RealityKit article, and the switch most people actually meet is Spatialize Stereo on AirPods. Whether the music side delivers is a separate question, covered in the Dolby Atmos Music comparison.
Future and challenges
The future of 3D audio is promising, but not without its problems. Despite the technological advances and growing interest, many people and media still struggle to navigate between the available formats and experiences.
“Still, it’s a good sign that it’s getting more and more coverage.”
The industry has to design these experiences so they are intuitive without a listener having to wonder which technology is running. That means seamless transitions between formats and content that holds up whether it is presented in stereo, surround or 3D.
I hope the terms are clearer now. The full episode is Spatial Realities Episode 43.
Frequently asked questions
What is the difference between spatial audio and immersive audio?
Spatial audio is a technical property: a position is rendered for your ears. Immersive audio is an experience and can even be stereo. One describes the signal chain, the other describes the effect on a listener.
What is the difference between spatial audio and 3D audio?
3D audio is about the content carrying height information. Spatial audio is about the playback rendering a position. A device can deliver spatial audio from material that has no 3D information in it.
What is the difference between spatial audio and surround sound?
Surround sound is speaker-bound and horizontal, tied to a room. Spatial audio is rendered for the listener and works on headphones anywhere.
What does spatial sound mean?
The same as spatial audio in most usage: sound rendered so that you perceive a direction. When a manufacturer uses the term, check whether the content is spatial or whether the device is simply upmixing stereo.
Is immersive audio the same as Dolby Atmos?
No. Dolby Atmos is one commercial implementation. Many immersive media cannot be reproduced in the AC-4 format at all, which is exactly the confusion this article exists to clear up. The format itself is explained in what is Dolby Atmos.
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