Dolby Atmos: the 3D sound experience

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Dolby Atmos is an immersive ‘surround sound’ system for the movies. It uses speakers at different heights to give an improved perception of space.

Recreating a theatrical experience in the home creates an interesting challenge for sound engineers. Cinema systems are meant for large halls and a number of people, but Atmos has translated to domestic use, with exciting results.

How does it work?

Dolby Atmos uses height channels – i.e. speakers placed above the listener’s head, not just at ear level. The result is immersion in a 3D sound space.

What does this mean for your audio experience?

By contrast with conventional surround sound, which operates on a horizontal plane, Atmos gives you the sense of the height and placing of each ‘audio object’. Imagine you’re watching a film of a plane roaring past. With Atmos, the effect is more nuanced; you can hear how close the aircraft is and how high. You may be watching 2D pictures, but surround sound tells your brain you are inside the story, not just witnessing it. It might be hard to imagine the difference, but trying Atmos at home reveals parts of the soundtrack you may never have noticed.

The technology behind the sound

Surround sound basically works by transferring sounds between different channels (speakers) and balancing respective volume levels. This gives a sense of movement, but Atmos does more; ‘metadata’ (additional information coded alongside the sound information) tells the speakers exactly where to put the sound. 

How many channels? This depends on who’s authoring the sound mix and the software used. For home use, the channel format is typically 5.1.2 (5 speakers, 1 subwoofer for low/bass effects and 2 ceiling or height channels) or more.

In the cinema Atmos can accommodate around 128 simultaneous ‘audio objects’ – from music to ambient effects to dialogue. Atmos for home use is adapted for a home environment; it enables enjoyment of the same soundtrack via a more limited number of channels. Soundbars also have an ‘upmixing’ feature to get more out of a conventional non-Atmos sound mix – and don’t forget that you can listen to music with an Atmos-enabled system too.

An Atmos-enabled soundbar contains all this capability in a relatively compact unit. Speakers are housed together as normal, but with the addition of upward-firing height channel speakers, usually on the top of either end of the bar. They bounce sound off the ceiling, instead of using ceiling-mounted speakers. Soundbars are the worry-free option, needing only an initial set-up, not precise placement of individual speakers.

Misconceptions about surround sound

Our Sony Europe technical specialist Eric Kingdon puts it best when he says, “some of the best sound mixes are also the most subtle.” Movie sound can be exciting and impressive, but it shouldn’t always be overwhelming. You should hear the difference between fine drizzle and a thunderstorm; the point is to achieve sound that’s natural and realistic.

Eric goes on to explain that surround sound is not always ‘behind your head’ as some people imagine, but enveloping you in a truly immersive sound experience. A metaphor for this is a surfer riding a wave; with Atmos, you’re inside it.

Find out about the Sony Atmos-enabled receiver STR-DN1080 and soundbar HT-ST5000.
Pair them with the UBP-X800 Blu-ray player, an ideal partner for 2K and 4K discs.