Autor: Karl M. Slavik

3D Audio

The field of application of 3D audio is highlighted in this article.

In stereophonic audio, the sound image is produced along an imaginary axis between two speakers and consequently has comparatively little audio image depth. To combat this recording via a binaural/dummy head can create a high quality soundscape. The delivery of binaural audio into traditional television sets is possible but created a unnatural viewing experience as each person needs to wear a headset.

Surround sound, either 5.1 or 7.1, provides a two-dimensional audio representation which provides a high degree of realism and spatial effect but it is still in one plane. These solutions still do nothing to provide a complete sound field. In 3D audio, “height” information is added so the sound can appear to come from above the audience. There is no “below” information so it is more “two and a half D” 

Designated channel formats for 3D audio for home use are referred to as 5.1.2, 7.1.4 and 9.1.2 – analogous to 5.1 and 7.1 for 2D surround audio. The number after the second decimal point (e.g. 2 in 5.1.2) is the number of channels as ceiling speakers. Home systems using object-oriented audio such as Dolby AC-4 and MPEG-H can support further options.

The main use of 3D audio is currently in the cinema environment with systems such as Dolby Atmos (object-oriented) and Barco Auro 3D. Dolby Atmos provides up to 128 ‘source channels’ for ‘Objects’ and ‘Beds’ that are rendered only within the cinema to a certain number of ‘physical’ speakers and where up to 64 channels are possible. 

Within the TV sector, Dolby AC-4 and MPEG-H are the most promising candidates to enable the next generation of 3D Audio.
For Blu-rays, Barco Auro 3D, and Dolby systems DTS-X and Dolby Digital Plus with Dolby Atmos, are especially interesting and where 9.1.2 is currently the maximum 3D audio format.

A well-crafted 3D audio production using an object-based method such as Dolby Atmos, Dolby AC-4 or MPEG-H can be rendered smoothly for playback in both the cinema and the living room with both locations having the possibility of different numbers of loudspeakers. 

A large number of distribution channels are required to deliver all the possible audio options of 3D, 5.1 surround sound, stereo and mono. The main problem with delivering 3D audio to the living room is that one should have 12 speakers or more but hardly anyone is willing to screw additional speakers to the ceiling.
Some manufacturers, such as Yamaha with the ‘Sound Projector’ YSP-5600 and Samsung with the ‘Sound Bar’ HW-K950 understand this situation and offer astounding quality and realistic 3D audio reproduction without speakers and cables hanging from the ceiling. There is also an option to have Dolby ‘Atmos-enabled’ speakers that point upwards to use the reflection possibilities of the living room space to emulate speakers on the ceiling, which allows a credible virtualisation of surround and 3D audio reproduction.

Author: Karl M. Slavik, Arte Cast Vienna

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