Understanding 3D Audio: The Immersive Technology You Should Know
- 21 Nov, 2018
Probably you not heard of 3D audio, but this is what we call sound technology and it has great potential. Did you know that it's over 130 years old? Today, amazing technology can be found in headphones and virtual reality headsets.
3D audio, or binaural audio, has come a long way, and it is amazing how many people have no idea that it actually exists. To many, 3D audio and surround sound is one and the same thing. But using these terms interchangeably is a sure way of amusing – or sometimes annoying – an acoustician.
So, to save you from this, let us categorically state that three-dimensional sound is quite different from surround sound. There are many factors that make the two different (we'll cover them in detail later in this article). But in the most basic terms, surround sound systems use several speakers to create a 360-degree field of sound around the listener. This gives a more immersive experience for watching movies, and is generally what you will find in theaters equipped with Dolby Atmos audio systems. It is also great for gaming and listening to audio, but not quite as much as 3D audio.
So, what exactly is 3D Audio?
Unlike surround sound that tries to create an immersive experience by placing speakers below, above, and around the listener, 3D sound recreates the natural sound you would normally hear when going about every day life.
It uses special recording techniques that mimic the placement of the ears on your head to capture sound like you would hear it. When played though high-quality speakers, the audio feels unbelievably natural. Those that have experienced it say that you hear the sound as if whatever you are listening to is happening round you and not coming out of a speaker system.
This new technology is now being applied to headphones and being used in more than just film. It is making music more immersive, and is expected to make Virtual Reality more fun than it has ever been.
How does 3D audio work?
As mentioned above, binaural audio gives you the impression that things are actually happening around you. If for example, a sound comes from the left, it is going to be heard louder by your left ear, and it will take a few milliseconds to get to the right ear. The change is subtle, but is sure makes a noticeable difference in the experience.
The brain uses different aspects of sound to determine its location and origin (sound scene). This is what creates the 3D sound. These factors include:
- Channel Crosstalk: When listening to a stereo's left/right configuration, the audio signal from the right speaker will reach both ears, and will be summed with the signal from the left speaker. When using stereo headphones however, the right ear only receives sound from the right channel and the left only receives from the left.
- Head and Ear Filtering and Delays: After sound has travelled through the air but just before it arrives in your eardrums, it is filtered and altered by your ears and the shape of your head. Sound therefore reaches your eardrumss at slightly different times, and with differing frequency shapes too. The length of the delay and filtration will of course, depend on where the sound originated from. When using earphones or headphones, no delays or filtration happens because the audio is delivered directly into your ears.
- Early Reflections: In the real world, or even in the barest recording studios, sound does not get to your ear directly from the source. It usually bounces off walls and other objects, creating a unique array of signals that get to your ears from different directions. In the industry, these are called early reflections. These sounds are then filtered and delayed depending on the direction from which they arrive at the ear. Your brain uses this information to approximate the distance and direction of the sound, and also the acoustic properties of the space you are in. When using headphones, none of this happens, and so there is no way for the brain to interact with the audio to recreate the physical environment.
- Head motion: All the factors above are greatly dependent of the direction the sound is coming from. This means that even the smallest movement of your head completely changes the audio scene because the external environment remains still. Luckily, the brain is sensitive and smart enough to know that it moved while the source remained stationary. It uses this information coupled with its memory of where the audio source used to be, and where it is now to create more accurate scene. Again, when using headphones, none of this happens because the audio scene is constantly moving with every motion of your head.
The brain uses all these cues to continually create a virtual environment that pinpoints the location and distance between you and the sounds you hear. Of course, the brain has evolved through millions of years, and is therefore, almost impossible to fool. When these sound cues are missing from the environment (as is the case when listening to music through headphones), your brain gets confused and will eventually give up on trying to locate the source of the sound.
This is why when listening to music or other sounds using headphones, the sounds feel as if they are coming from within our head. All elements of the sound are crowded into a 2-dimensional space between the right and left ear, and not a 3-dimensional space as it is in nature.
3D audio music however, tries to recreate the sound in a close to natural way as possible. You therefore hear sounds just as you would in real life when using 3D audio headphones as compared to surround sound headphones.
Why is 3D audio so popular? What are its benefits?
Virtual reality headsets like Google Cardboard and others have made virtual reality bigger than it ever was. The biggest driving force for the development of 3D audio at the moment therefore, is virtual reality. The logic behind it is,‘if it is possible to create a completely immersive virtual world, why not couple it with 3D sound too?'
The biggest branches of VR that are at the forefront of 3D audio music development are:
- The Gaming Industry: With more and more VR headsets finding their way into the gaming industry, gamers are preferring an environment that provides the most accurate representation of the games they are playing. 3D sound gives the gamers a complete view of their gaming world that extends beyond what they can see. It makes it possible to interact with their team members with ease and accuracy. They can know the direction of friend or foe just by listening to the sound of their footsteps, or the origin of their gunfire.
- The Marketing Industry: The marketing industry has also found numerous uses for virtual reality technology. Companies now want to give their users an experience of how their products would look like under different situations. 3D audio takes this experience a notch higher by boosting how immersive and real these situations can be.
3D Audio vs. Surround Sound: What's the Difference?
You most probably already understand what makes 3D audio so special. But what really makes it so different from surround sound? What makes listening to audio 3D sound, or using 3D headphones so different from the surround sound experience of movie theaters or home entertainment systems?
Well, the biggest difference lies in how the sound is recorded.
The arrangement of a surround sound speaker system and a 3D audio speaker system is not very different because most of what makes the two sound systems different happens during recording.
Traditionally, recordings can either be done using mono or stereo methods. Mono only uses one microphone to pick up sound for recording, while stereo uses two microphones spaced some distance apart.
Binaural or 3D recording takes this a step further. Two microphones are placed in ear-like cavities and placed on each side of a dummy head. The sound recorded in this setup is therefore, exactly as it would be captured by a human ear. It goes through all the reflections, filtering, and delays as in a real human ear, thus preserving its interaural cues.
The best way of experiencing 3D audio or music, is therefore by use of headphones that have a clear distinction between left and right channels.
The concept behind 3D audio is quite simple, but when recorded through high quality microphones and played over high quality headphones, the experience is truly magical.
Even though this is not yet mainstream, it is expected that in the next few years, there will be major strides in this industry. We cannot wait for the time to come, when listening to music over the headphones will be as magical as watching a live performance from the front row, or when playing a virtual game will be as realistic as being inside the game.