Portable Immersive Audio: How 3D Headphones Work
Exploring the science behind 3D headphones, and anticipating their fascinating future potential.
By Ben Jacklin
When you think of an immersive audio setup, you probably think of five, seven, or even more speakers. Many of the top home setups involve a number of satellite speakers and precise positioning to perfect the audio playback.
So, you might assume that immersive audio and headphones don’t mix. Surely you only have a left and right channel to play with?
Clever technological advances have spurred advances in headphones, enabling them to replicate the sound and feel of a 360-degree sonic field, giving the illusion of true immersive audio from just two channels. So, how do these “technological advances” work?
How Exactly Does Immersive Audio “Work” in Headphones?
The science behind this is certainly complex, but this high-level overview will be a good place to start.
The technology within your headphones is likely binaural, meaning you will only be working with two directions of sound. To overcome this limitation, the technology driving the 3D field has to be incredibly dynamic.
The immersive effect is achieved by creating a “virtual space.” The audio is set to play as it would in a room. However, instead of directly hitting your eardrums, the illusion of reverberations bouncing off items and coming from other directions is created by altering frequency response and delay. Headphones dexterously mimic how a sound wave would arrive from a speaker in the distance rather than simply pushing audio straight into the listener’s ears.
For those interested in reading more on this phenomenon, the convolution of sound waves is called head-related transfer function or HRTF. Basically, the shape and density of your head has a meaningful impact on the acoustics and frequency response, and can even transform the way your brain perceives sound.
The brain does an incredible job of memorizing how your head impacts perception of sound. Every ‘obstacle’ (part of your head) can change the sound slightly and give us a different impression of where the sound has come from. These obstacles include the shape of the listener’s outer ear, the shape of the listener’s head and body, the acoustic characteristics of the space in which the sound is played, and so on. All these characteristics will influence how (or whether) a listener can accurately tell what direction a sound is coming from.
The brain memorizes all this and uses these signals as an indicator of where sound is coming from. This is ultimately what gets manipulated to provide a wider stereo field and the illusion of immersive audio.
3D headphones will also track your head position. When experiencing audio coming into the ears, the brain makes tiny movements and adjustments to sense where it is coming from and to what direction it is traveling. This is an evolutionary development to aid spatial awareness. The technology within headphones such as Waves’ 3D Audio and Sennheiser’s Ambeo mimic this phenomenon of monitoring and responding to head movements to create the feeling of sound arriving from different areas of the stereo field.
The Future of 3D Headphones
Already, some headphones can track your head movements to better provide a HRTF experience. In the future, it is expected that these headphones will be able to work out the dimensions of your head, providing an even more personal listening experience.
Binaural sound recordings are embracing this innovative technology; even mobile phones are starting to utilize binaural sound for 3D audio effects.
It all sounds like something from a science fiction film. The Verge described 3D headphones as a way of “hacking your brain”. Similar to how 3D visuals alter our brain’s perception to give the illusion of an extra dimension, headphones can do the same for music, gaming and movie fanatics who crave a more immersive experience from a more compact system.
About the Author
Ben is a writer and musician from the UK with a background in music technology. He writes about engineering and production, musicianship and music equipment for a number of publications including his own site, subreel.com