Tech Corner 3: Binaural Sound

Binaural Sound. What is it?

Binaural recording is a method of recording sound that uses two or more microphones. Instead of the traditional stereo mixing, where audio is balanced between the left and right channels, binaural sound uses these same channels to produce a three-dimensional audio space. So instead of hearing things simply on the left or right, audio is deliberately made to sound as though it is coming from the full 360 degrees of the listener’s hearing. Footsteps would be heard underneath, the tweeting of birds would come from above, and so on.

It can enhance a listener’s experience by offering a more diverse, and immersive experience. This can amplify the tension in scene, or bring an environment to life, alongside a number of other functions. It also makes sound effects a lot more dynamic, particularly for something like a vehicle moving across a scene.

How does it work?

The recording process usually involves the use of more sophisticated microphones, positioned strategically across the set. By doing this, the speech from actors can be better weaved into a 3-D experience when mixed. Alternatively, producers can use a dummy-head, a mannequin with two microphones where its ears are, to imitate the way sound would be heard by a listener. This added expense and complication is a large part of why binaural sound hasn’t been widely adopted.

Another issue is that binaural sound is somewhat dependent on the quality of headphones used. Cheaper earphones are notoriously poor at picking up lower end bass-y sounds, so to counteract this these would need be shifted up in pitch in post-production. But on more high-end gear this can make things sound artificial, and a bit off, resulting in a ruined effect.

Far from a cutting-edge technology, binaural sound was first demonstrated in France in 1881, through a concept called “Théâtrophone”. This service allowed subscribers to listen to opera and theatre performances through two separate speakers, held over each ear, at various locations across Paris. While this didn’t have the polish or technology needed to make the most of the effect, it was the foundation of what is used today.

What is it for?

Unfortunately, use of Binaural sound has been slow at best. Due to the complications with recording audio, and the current requirement for headphones to achieve the best affect, this is unlikely to change overnight. An ideal fit for this technology would be gaming, but as it stands it’s not the priority in favour of graphical improvements. It has seen limited use in games like Battlefield 4, but developers have yet to widely adopt it. The applications for binaural sound in Virtual Reality have barely been tapped into, and increasingly companies are noticing that it could be the next big jump for immersion. For VR developers targeting realism with their visuals, the audio element would be the logical next step for tricking the senses.

The technology also has applications now that 360 video has become more popular. One of the main limitations of 360 video as it stands is that the audio is almost always recorded from a fixed point, meaning that while you can look freely round an environment, you can’t hear exactly where you’re looking. The introduction of binaural sound would complete the 360 effect, by allowing people to hear exactly from the perspective they are viewing.

In May 2017, the BBC broadcast an episode of Doctor Who with binaural sound, largely as an experiment for the Research and Development division. The BBC has experimented with binaural audio in the past in a number of different formats, and are one of the rare broadcasters to recognise the potential application for the technique. The episode, titled “Knock Knock”, used the technique to create a tense, almost stressful experience that’s strangely compelling. That same edge-of-your seat feeling you might get watching a horror film, was achieved and arguably bettered in a family oriented sci-fi show.

Do you want to see more binaural content TV and films, or are you not convinced this tech will ever catch on? Let us know in the comments.