3D Audio Formats in Film Scoring

Recent years have shown quite dramatic technical advancements regarding immersive playback of movies. And while the 3D projection seems to have been a phase that hasn't been as enthusiastically received by the audience as the manufacturers might have hoped for there has been quite a development regarding sound playback.

More and more cinemas as well as home theatres are being equipped with so-called 3D audio formats. All have in common that from the two dimensional plane of a 5.1 (or 7.1) signal where the speakers are arranged in a horizontal way around the listener, speakers get added above the listener's perspective providing sound from above.

While this seems rather "gadgety", it indeed has a quite profound impact on the realism of sound reproduction. Of course, overhead helicopters and thunderstorms come to mind but for the film and media composer, this whole development has another interesting quality.

While thankfully the days are gone where you would move instruments around the listener just for the sake of it, 3D audio formats help alot to add depth and space to the music.

In a recording of an orchestra or a concert, half of the sound is defined by the space. Reflections of the sound coming from the back walls, the ceiling etc. tremendously shape our spatial perception of the music and the more accurate this can be reproduced the more realistic and immersive the listening experience will be. In a musical genre where we need to create the maximum emotional impact, transporting all nuances of the music to the listener is a big bonus.

There are currently three different formats competing on the market:

Dolby Atmos:

Dolby has developed an object based format. This means, it is independent regarding the amount of speakers. The source of a sound is placed in a virtual sphere and the local system calculates which of the speakers that are available in the playback situation should play back the sound. The downside is that all reflections of that sound within the space need to be artificially calculated by the system and placed accordingly in all the other speakers in order to create a believable sound experience.

Auro 3D:

Developed in Belgium, this system is channel based, meaning that there is a discrete signal for each speaker. The advantage of this is that you can reproduce the natural sound of an acoustic event as you can record it with a microphone setup that is analog to the speaker setup. The downside is, that you MUST have this speaker layout as close as possible to its specification to reproduce this.

DTS:X:

This is a format developed by DTS that is designed to have the highest flexibility to work with any existing speaker setup. However it hasn't gained that much traction in the market yet.

The problem with Dolby Atmos and Auro 3D is that they are not technically compatible. The specifications of the speaker arrangements differ that even if you had both signal processors the different placement of the speakers would not allow to run both systems simultaneously. In the home cinema market there are a few possibilities to run all 3 formats on the same system, however only with technical compromises.

Currently, it seems like Dolby is winning this technical battle, mainly because streaming providers like Netflix and Disney+ have adopted this technology into their playback options but also because more theatres are being equiped with a Dolby Atmos system than an Auro3D System.

From the film music standpoint both systems work equally well. The usual way to create a 3D audio film score would be to base it on a Quad mix. This means a stereo channel plus two rear channels that you could source for instance from the rear microphones. This signal usually gets blown up by adding a digital reverb that creates the 3D audio accordingly.

However, there is also a possibility  to natively record a score in a 3D format.

In 2018, I wrote the score for a feature film that was released in Dolby Atmos. As I knew the target format well in advance, we decided to record the orchestra natively in Dolby Atmos. Additionally to the regular microphone setup that you would have, we used a "Heighth Array" microphone in the room with four directional microphones positioned above the conductor pointing towards the studio ceiling to capture the reflections from there. In the mix we positioned these reflections accordingly in the virtual sphere to recreate the room reflections. The possibility to automate these signals and open up the space in "grand moments" and narrowing it down in other moments really had quite some impact on the creative possibilities we had with the music which really benefited the overall experience.

Whether it is necessary to natively record the heighth information or to generate it with a digital reverb might be debatable but it was a nice experiment.

The bottom line however is that you should be aware of these developments and also be aware of the fact that you can use these formats to create a more immersive musical experience.

Personally, I would always use these possibilities if budget and technical prerequisites allow as it really opens up a wider palette of expressiveness.