Immersive Audio: AES Day 3

What do you call surround sound that uses more than the usual 5.1 or 7.1 channels? Is it 3D Audio? Not according to the NATO (National Association of Theater Owners) and the AES. The new name is “immersive audio” and Sunday’s conference sessions were all focused on this next generation theatrical sound delivery experience. The opening keynote address was delivered by Francis Ramsey. He gave a very thorough overview of the recent trends in immersive audio and traced the introduction of Auro 3D, Dolby’s Atmos system, and DTS’s MDR format. It was not a coincidence that all of the AES sessions were held in a theater equipped with ceiling mounted speakers.

The morning papers sketched out a few of the major topics and included “Properties of Large-Scale Sound Field Synthesis” presented by Jens Ahrens from the University of Berlin. His paper focused on the difficulties in recreating real world sound using arrays of speakers. It turns out that low frequency sounds are relatively easier to reproduce than frequency higher than about 500-100 Hz. The interference patterns and reflections from the acoustic space cause all sort of problems.

The next paper was about “nouvOson: How a Public Radio Broadcaster Makes Immersive Audio Accessible to the General Public”. The presenter was Herve Dejardin. In March of 2013, Radio France launched a new part of its website, called nouvOson (for New Sound), to broadcast binaural and 5.1 surround sound. The binaural format was chosen to support listeners that don’t have domestic 5.1 surround systems. The paper described how Radio France developed their application and how they support the delivery of both audio formats. The presenter didn’t discuss where the multichannel source material was coming from. I suspect that classical orchestras and other non-commercial producers of surround music are supporting the site. There just isn’t any pop/rock recordings being mixed in surround…or certainly not enough to keep a website stocked.

The next paper was about Ambisonics and was presented by Matthais Frank of the University of Music and Performing Arts in Graz, Austria. “Ambisonics is a 3D (should it be called immersive now?) recording and playback method that is based on the representation of the sound field excitation as a decomposition into spherical harmonics”, according to the blurb in the AES handout. This methodology has been around for a long time, I experienced in almost 10 years ago when I gave a paper at a 2007 London AES conference. The presenter discussed current trends in Ambisonics and a VST plugin that allows engineers to work with it in their own Digital Audio Workstations. The really cool thing about Ambisonics is that the recordings can be completely re-tweaked during postproduction. Following the presentations, the audience got to hear a demonstration of Ambisonics.

I have serious doubts about the viability of “immersive audio” as it pertains to theatrical sound…and apparently so do movie patrons. In a recent survey of moviegoers, most couldn’t tell the difference between normal surround 5.1 theatrical sound and the new and improved “immersive” enhancements. Theater owners, movie studios, and postproduction houses will need to adjust their workflow and delivery strategies if this manages to take off.

Several professionals discussed this very issue on a panel. Which system will dominate, how can they simply DCP (digital cinema packages) deliveries, and what are the advantages and disadvantages of going “immersive”? Time will tell.