Whether you’re video conferencing, streaming music, or gaming, the quality and realism of audio can make or break your experience. For decades, stereo reigned supreme. But today, new terms like Spatial Audio, 3D Audio, and Immersive Audio are entering the mainstream, promising to revolutionize how we perceive sound. While often used interchangeably, these terms reflect a broader evolution of audio technology, one driven by a deeper understanding of human hearing, perception, and the desire for ever more realistic experiences.
From Stereo to Surround: The Early Stages of Spatial Audio
Traditional stereo setups utilize two channels, left and right, to create a horizontal soundstage. Though powerful when used creatively, stereo’s effectiveness with speakers is limited by its dependency on a listener’s position relative to the sound source. With headphones, the position is fixed, but spatial realism still relies on psychoacoustic cues. Classic recording and rendering techniques such as mid/side (M/S) or intensity stereo exploit psychoacoustic effects to enhance spatial cues, but they still require a “sweet spot” for optimal perception.
The development of surround sound, most notably 5.1, marked a major step towards enveloping the listener. By adding more loudspeakers, typically in a horizontal ring around the listener, audio could be positioned not only to the sides but also in front and behind. While this configuration significantly improved immersion in home theaters and cinemas, it still left out one critical element: height.
Spatial Audio and the Third Dimension
To address this limitation, researchers and developers introduced spatial audio, sometimes called 3D audio, which extends sound reproduction into the vertical plane. Spatial audio introduces elevation, allowing sound to be perceived from above or below the listener, and is especially useful in formats designed for headphones or virtual reality applications. The dominant method for reproducing spatial audio over headphones is binaural rendering, which simulates how sound arrives at the ears using Head-Related Transfer Functions (HRTFs).
However, binaural audio alone often falls short of truly immersive experiences. Without personalization and environmental awareness, the sound may still seem to come from “inside the head,” rather than from the surrounding space. While early implementations of spatial audio offered a taste of 3D, they lacked the externalization and movement-responsive behavior needed for full immersion.
A comprehensive review titled Surround by Sound (2017) outlined two major pathways to spatial audio: binaural approaches, which model how sound reaches our ears, and sound field reproduction, which aims to reconstruct entire acoustic scenes using a setup of microphones and loudspeakers. Both strategies have shaped today’s immersive formats, but they differ significantly in how sound is delivered and experienced.
Immersive Audio: Going Beyond Perception
True immersive audio moves past mere directionality to create a sense of being in a plausible acoustic environment. It integrates realistic room acoustics, head and body tracking, and dynamic sound rendering to achieve a level of audio plausibility that can fool the brain. Listeners don’t just hear sounds, they perceive them as existing in real space, anchored to their surroundings even as they move.
Demonstration of 6 degrees of freedom (6 DoF) in a three-dimensional space
Unlike stereo or even surround systems, immersive audio doesn’t rely on a fixed sweet spot. Instead, it allows users to turn, lean, or walk through a virtual scene while the sound field responds accordingly. This requires 6 degrees of freedom (6 DoF), capturing not only head rotation but also positional shifts. To achieve this level of realism, systems often use Binaural Room Impulse Responses (BRIRs) that combine individualized HRTFs with the specific acoustics of a virtual room.
Recent studies show that adding accurate room acoustics and tracking to binaural audio significantly improves listener immersion. In fact, in one study involving VR users, participants rated experiences with head-tracked binaural sound and realistic room reflections just as highly as those with video quality five times higher, highlighting the often-underestimated role of sound in presence and realism.
Technologies That Power Immersion
Modern immersive audio systems rely heavily on object-based audio formats such as Dolby Atmos, MPEG-H 3D Audio, and Auro-3D. These standards use metadata to define not only what a sound is but where it should appear in 3D space, making them adaptable to different speaker setups and compatible with headphone playback. When combined with wave field synthesis or higher-order ambisonics, these formats can recreate realistic, room-scale audio environments where sounds remain fixed in place no matter where the listener moves.
However, immersive audio is not just a technical challenge; it also requires creative innovation. A 2022 review by Turner et al. highlighted that while tools and frameworks for immersive audio are emerging, many workflows are still underdeveloped. Creating believable soundscapes for VR or AR involves not only mastering new software but also understanding how listeners interpret spatial cues in complex, dynamic environments.
Our Contribution at Brandenburg Labs
For over 40 years, researchers have worked to recreate this level of immersion through headphones, striving for what’s known as the “perfect auditory illusion.” Despite many proposals over the decades, most have fallen short of delivering a fully convincing experience.
At Brandenburg Labs, we are proud to be writing the next chapter in this story. With our cutting-edge Deep Dive Audio technology, we’ve developed a headphone-based system that delivers a plausible, externalized, and stable immersive audio experience. Our system has been experienced by over 1,000 audio professionals and enthusiasts worldwide, consistently delivering impressive results. We’re committed to shaping the future of audio, developing technologies that bring lifelike, interactive, and immersive listening to everyone, everywhere.
Resources
Neidhardt, A., & Zerlik, A. M. (2021). The Availability of a Hidden Real Reference Affects the Plausibility of Position-Dynamic Auditory AR. Frontiers in Virtual Reality, 2, 678875. https://doi.org/10.3389/frvir.2021.678875
Potter, T., Cvetković, Z., & De Sena, E. (2022). On the Relative Importance of Visual and Spatial Audio Rendering on VR Immersion. Frontiers in Signal Processing, 2, 904866. https://doi.org/10.3389/frsip.2022.904866
Turner, J., Simpson, A. J., Garcia-Garcia, J., & McGregor, I. (2022). The effect of audio on the experience in virtual reality: A scoping review. Behaviour & Information Technology. https://doi.org/10.1080/0144929X.2022.2158371
Werner, S., Klein, F., Mayenfels, T., & Brandenburg, K. (2016). A summary on acoustic room divergence and its effect on externalization of auditory events. In 2016 8th International Conference on Quality of Multimedia Experience (QoMEX) (pp. 1–6). IEEE. https://doi.org/10.1109/QoMEX.2016.7498973
Zhang, W., Samarasinghe, P. N., Chen, H., & Abhayapala, T. D. Surround by Sound: A Review of Spatial Audio Recording and Reproduction. Applied Sciences, 7(5), 532. https://doi.org/10.3390/app7050532
