Welcome to ‘Kagoo Explains’ - a series of short articles de-mystifying some of the confusing terminology used to describe tech. This week we’re looking at ‘Dolby Atmos’ - a sound technology used to give your movies a sense of height!
If you’ve read our article on Virtual Surround Sound, you’ll be familiar with the term ‘Dolby Atmos’. It’s a very exciting technology that seeks to improve 3D Audio by adding ‘height’ to an audio mix, allowing a full surround sound experience. This system is used extensively in cinemas to give total immersion to patrons, but the last few years have seen a move towards Dolby Atmos systems for home cinema setups, and even for small soundbars!
First, let’s look at the tech itself. Dolby Atmos uses a special mix of a movie’s audio tracks and various audio trickery to make it sound like certain noises are not just coming from the left or right, but also moving around the listener - and over their heads too, adding height to what was previously a purely horizontal experience.
The key to this is something called ‘Object-Based Audio’ - this is the idea that in addition to the standard ‘flat’ audio track for a movie (containing the music, dialogue, etc.) there are additional tracks for specific individual sounds - known as ‘objects’. These objects are tagged with positional data - effectively telling the system where the object originates, how fast it’s ‘moving’, where it stops, etc. This allows the objects to ‘move’ through an audio mix - meaning Object-Based Audio can help to create a powerful sense of immersion and place to a movie soundscape.
EXAMPLE: So if you're watching a scene of someone driving, there could be a passing car which starts behind the camera (the centre of the sound), before overtaking to the left and zooming ahead.
In terms of the surround sound, this means that the object 'passing car' would start being played only in the rear speakers, before transitioning to the left speaker, and finally moving to the front speakers before reducing in volume as it moves away.
From the cinema to your home
These mixes must be created specially, and can’t be understood by every sound system - only Dolby Atmos-compatible systems have the capacity to decode the positional data attached to the objects, and process the complete scene so everything is in the correct place. It requires some effort to set up, but the results are astounding - a massive improvement on previous attempts at surround sound.
As mentioned above, this is not limited to the horizontal plane - the objects can also be given height, and projected in a way to make it sound like they are above you. In full cinema setups, this is achieved by placing speakers in the ceiling of the auditorium - which allows filmmakers to create the illusion of a helicopter flying over the heads of the audience. Understandably, this is a dealbreaker when creating a home theatre setup, unless you want to really commit and start ripping open the walls!
Few people want to go to those lengths - and landlords really don’t like it - so instead home audio designers have come up with a clever alternative: upward-facing speakers. As the name suggests, these fire the sound upwards and bounce them off the ceiling towards your ears, giving the illusion the sound is coming from directly above you. They aren’t quite as effective as properly-installed ceiling speakers, but they are far easier to set up!
5.1 vs 5.1.2
When advertising sound systems, manufacturers love using impressive-sounding numbers - 3.1, 7.2 or 5.1.2. While they look confusing, these just describe how many speakers make up the system - the first number is for the amount of ‘main’ speakers, while the second is the number of subwoofers (bass speakers that handle the very low register of an audio mix).
When looking at 3D audio and Dolby Atmos, a 3rd number is added - this tells you how many positional speakers make up the mix. So in a 5.1.2 sound system, there are 8 speakers: 5 handle the majority of the sound, 1 subwoofer takes the bass, and 2 upward-firing speakers add height to the mix.
Small... but mighty
For those who want to go smaller still, all of this technology comes together in the new generation of Dolby Atmos-supported soundbars. They make full use of Virtual Surround Sound and Object-Based Audio to give the illusion of 3D audio, and have an impressive presence and sound quality, especially when compared to a full 8-speaker home theatre setup. These soundbars usually have the upward-firing speakers built into the main soundbar - possibly with a separate subwoofer or a pair of side speakers for extra power.
So, we can see that not only is Dolby Atmos capable of adding a sense of height and increased immersion to your movies, but it is also more readily available than it ever has been - you can set up a full home theatre for under £1000 or grab a powerful soundbar that can do it all in a small package. Whatever you choose, you’ll be getting a cinema-quality 3D sound from the comfort of your couch.