What is 3D Audio ?

3d Audio Sound

3D Audio Sound (or 3D Sound) perception is the capability of the human auditory system to locate sound in space and more widely, to be aware of the acoustic structure of its surrounding environment. It is the natural way we listen to the world.

The spatial sound perception provides us with several key elements: sound direction and distance, type of location (indoor or outdoor, large or small room, material of the walls and ground …), number of sounds, sound source discrimination (cocktail party effect: we perfectly understand somebody talking in a noisy environment including several people talking).

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How do we hear in 3D with only two ears?

The auditory system uses the combination of 2 types of information to localize a sound: Binaural Cues (Time and Level) and Head Related Transfer Functions (HRTF).

 

Binaural Cues

When a sound source is located eccentrically, it is closer to one ear than the other and sound arrives later and weaker at one ear. Time and level difference perception between the two ears provide information about direction. These binaural cues are called Inter-aural Time Difference (ITD) and Inter-aural Level Difference (ILD). They are important for the horizontal localisation.

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HRTF

Before reaching the entrance of the ear canal, a sound wave coming from one direction is transformed by the multiple reflections on our body, our face and more importantly our ears. This transformation, called Head Related Transfer Function (HRTF), is different for each direction of sound and has a specific spectral signature for each direction. The brain has “learned” these signature over time and when it hears a sound with a specific signature, it can find out its direction in its HRTF memory. HRTF is important for vertical localization.

Of course, all these cues change with the direction of the head. That is why head movements, even very small, are so important to 3D audio perception.

 

Binaural Synthesis (aka VR Audio)

3D Audio Sound : High Order Ambisonics

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Amon 3d Audio Sound, Binaural Synthesis is the process of reproducing synthesized sounds called binaural audio, effective at the entrance of the ear canal with the proper binaural cues and HRTF to make the auditory system believe these sounds are real.
Like virtual reality headsets which fool the visual system by showing synthesized images to the eyes, headphones can fool the auditory system with binaural audio at the entrance of the ear canal. When binaural synthesis is combined with head tracking, it becomes Virtual Reality Audio.

If you want to learn more about the audio formats used for Virtual Reality, have a look at this blog post.

 

3D Sound Labs VR Audio Engine

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Our R&D team has developed a VR audio solution with advanced binaural synthesis and head tracking with the key features for best in class performance.

 

High Order Ambisonics

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3D Sound Labs VR Audio engine processes sound in the spherical harmonics domain called High Order Ambisonics (HOA). This powerful mathematical representation enables our VR Audio Engine to do very fast and smooth head tracking processing and to render a very immersive and realistic 3D sound image. For developers, the scalable nature of the HOA paradigm also allows for easy CPU load management for a large number of sound sources, platform variability and battery management.

Low Latency Head tracking

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Because our auditory system heavily relies on large and small head movements to locate sounds, low latency head tracking is absolutely key to good 3D Audio rendering. 3D Sound Labs uses the capability of its Higher Order Ambisonics VR Audio engine and 9DOF motion sensing module to provide a precise and low latency head tracking solution.

Spatialized Reverberation

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3D Sound Labs VR Audio engine has an advanced “Room Model” that provides the capability to spatialize the early reflections and calculate a late reverberation consistent with the acoustic environment. Realistic reverberation processing is very important to the perception of 3D audio. Early reflections provide additional key information on the distance of sound as well as on direction. The late part of the reverberation, which depends on the acoustic environment, needs to be consistent with the visual environment in order for the human auditory perception to experience a realistic “Presence” in a sound scene.

Headphones Equalization

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Equalized headphones with a flat frequency response can reproduce 3D sounds more naturally and with more accuracy. Therefore, to optimize 3D audio perception with 3D Sound ONE headphones, 3D Sound Labs VR Audio engine uses a specific equalization when these headphones are used.

 

 

3D Audio Sound : End User HRTF Individualisation

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Head Related Transfer Functions depend on the shape of your body and because everybody is different, perfect 3D audio rendering implies using a set of HRTF different for each end user and which is adapted to the morphology. For good externalization and vertical localization, the size of the body part (head, torso, …) are not relevant. What matters is the actual shape of your ears!
The 3D Sound Labs R&D team is working on a disruptive way to personalize your HRTF in an end user friendly way. We are so excited to show you what we’re building, so while we work to get it exactly right for you, please keep in touch and know that perfect 3D audio is right around the corner.