SURROUNDED: DOLBY ATMOS and 360º REALITY AUDIO
Or shortly about surround systems and headphones

⌈ The dream of the sound that would not be a flat representation projected by the speakers in front of us has existed since there have been devices for its reproduction, and even longer. Only recently has it become common practice to publish albums simultaneously in stereo and multichannel formats. And not only for listening through loudspeakers, but also through headphones. The following text is just about listening to surround sound through headphones. ⌋

REAM OF A SOUND SURROUNDIGN LISTENER is part of the history of music. Parts of the organ located in different places of the church, musicians and singers' sections placed in various places in concert halls by composers, the efforts of directors of musical performances, and nowadays also the presence of loudspeakers around the concert halls - all this was supposed to bring us closer to the ideal of "immersing" us in sound. It was supposed to take us into a different reality.

▌ SURROUND

HOWEVER, IT SO HAPPENS that a breakthrough in this field was brought about by cinema, a medium tens of thousands of years younger than music. The surround sound, translated in the Polish specialist press as "multi-channel sound", added special effects to the picture, also ones coming to viewers from behind their heads. The music scene had to wait much longer for its time, because until the beginning of the 1970s. The Quadrophonic sound was a - I would say today - 4.0 system, i.e. a four-channel one, with two additional loudspeakers placed behind the listening position.

⸜ Studio Dolby Atmos – Blackbird Studio in New York • photo Blackbird Studio

This idea didn't really work out because there were several incompatible systems competing with each other, few customers wanted four speakers at home, and most of the recordings were focused on effects, not music. In the cinema, however, surround sound made a stunning career, and as soon as it was possible, it was brought into the home environment. The resulting "home theater" systems had much in common with cinema, but sold well. The sound evolved in it similarly to real cinema, that is, increasing the number of channels, switching from analogue to digital recordings, establishing the 5.1 scheme, then extending it to 7.1, as the "standard”.

Everything that I’ve been writing about above was a logical consequence of striving to establish a solid "stereophony", understood as a "spherical" sound. Techniques, the number of channels, etc. changed, but the core, that is, surrounding the listener with speakers, each of them playing monophonic tracks, was a constant. The longing for surround sound also touched those who listened to it using headphones. However, quadrophonic models turned out to be impractical, and although the attempts were surprisingly frequent - nothing came of it.

Listening through headphones already had a developed method of transmitting sound "in the sphere", or at least in an omnidirectional way - I am talking about BINAURAL sound (you will find more about this technique in the Binaural. 120 Years Of Headphone Kingdom , HF № 140 , December 1, 2015, HERE). When smartphones took over the function of music players and young people began to use headphones on a large scale, it seemed that the golden times for binaural sound are about to come. It did not happen. It seems that the difficulties related to the recording and processing of this type of signal deterred the main actors, i.e. streaming services, from this idea.

When it seemed that there idea of a “surround” sound with headphones was dead, there came another big change in home theater that changed things in a way. I am talking about the DOLBY ATMOS system. This is the latest audio coding system from Dolby Laboratories, in which to up to five or seven (or nine) channels arranged in a horizontal plane, also channels in a vertical plane have been added. The idea itself is not new. As early as in 1970, Karl Stockhausen presented his sound installation Kugelauditorium, and in 1973 the pioneer of the Ambisonics system, Michael Gerzon, suggested a practical solution to the problem using four channels.

Interestingly, the signal informing about the placement in terms of height of a given sound source was conceived and then developed in music playback circles. It was not until 1999 that Tomlinson Holman demonstrated the "10.2" system, intended for the cinema, with two front channels with "height" information, i.e. in the 'y' axis. In audio, the Belgian engineer Wilfried van Baelen saw his chance, and in 2005 he developed a system known as 2+2+2, and over time developed it into Auro 3D, which is used today by several companies, including 2L.

But nothing compares to the power with which the perception of "spherical" sound was introduced by the Dolby Atmos system. It is a different system than almost all the previous ones - with the exception of the Ambisonic. It is based on "objects" and not "channels" - this is the so-called object- based system (all others are channel-based systems). The point is that while in the other systems each channel has a separate mono track, with stereo reverbs between the stereo pairs and delays between the front and back, in Atmos all channels are in some relationship with the others and you can talk about the actual placement of the object in space.

▌ HEADPHONES

EVERYTHING THAT WE TALKED ABOUT concerns listening tu music using loudspeakers. What about headphones? In 2008, the audio engineer Joern Nettingsmeier in his work entitled The Why and How of With Height Surround Sound said:

Headphone binaural systems can deliver a perfectly convincing illusion of height with outstanding quality, but head tracking systems for the required third axis are not yet widely available, and in addition to achieving perfect results individual HRTF measurements are required for each listener.

While the problems with adjusting the sound to the individual structure of the ear (HRTF) is still an unsolved problem, the systems for playing spatial music, along with information about the height, are already available for everyone. The "game changer" turned out to be the introduction of Dolby Atmos files to the offer via the Apple Music streaming service. On June 12th 2021, at the WWDC 2021 conference, Apple announced a "spatial audio" program for its service, and company director Eddy Cue said it was like "switching to HD image on TV."

⸜ Tidal has been offering Dolby Atmos files for over a year

While the system itself has been known for years, also systems such as Dolby Surround, which "created" spatial from stereo material, existed, but this time it is different. This is because everyone who has a smartphone can use the benefits of Dolby Atmos. Even my old Samsung A41 can play such files after updating the software. They are available, for example, on the Tidal - they announced their decision on July 2nd 2020 (more HERE; accessed 09/24/2021).

Although Dolby Atmos novelties are not displayed on the main screen, the menu has a tab for albums encoded in this way. And there are a lot of them and the choice is wide because they come from two main sources - Universal Music Group and Warner Music Group.

This market seems so attractive that Sony also presented its offer, and they own catalogs of such record labels as, for example, Columbia Records. Its engineers developed an omnidirectional system called 360º Reality Audio. Spatial encoded files in this format can be found on Deezer, Tidal and nugs.net, as well as Amazon Music HD. Tidal shows it alongside Dolby Atmos, on the menu. Contrary to the latter, we are talking about classic surround sound without any height information. But there is something the competitor does not have.

⸜ Same as with Dolby Atmos, with the 360º Reality Audio sound arrives to us in X-Y and Z axes • photo Sony

Do you remember the problems with HRTF? Head Related Transfer Function talks about how the sound is changed by the shape of our ears and the head in general - each of us perceives it differently. In order for the surround sound in the headphones to be as credible as possible, the signal should be encoded so that all parameters match perfectly. In practice, it is impossible, so when encoding Dolby Atmos you do it by averaging many measurements. Sony does it a bit better. It offers a special Headphones Connect application, in which we take a photo of our ears, and then it introduces corrections to the 360º Reality Audio decoder that adjust the signal especially for us (more HERE; accessed: 24/09/2021).

▌ SOUND

ALBUMS CODED IN DOLBY ATMOS and 360º Reality Audio have been available in Tidal for a long time and I have been listening to albums of my choice almost from the very beginning. For the purposes of this text, for a week I listened only in this way, using the already mentioned Samsung smartphone with an external D/A converter ALO AUDIO PILOT |PL|, with the USB application AUDIO PRO, via LIME EARS PNEΠMA headphones.

⸜ The system used for the audition

The conclusions from these auditions are ambiguous and my impressions are mixed. The transition from stereo to surround recordings, no matter in which system, involves a complete change of perspective - it is truly omni-directional sound that surrounds us from all sides. The sound has to be louder as this type of signal has a lower amplitude, but after adjusting it - I prepared a playlist with the same tracks in stereo and surround - everything returns to normal.

I had a great time listening to the first few albums. "This is finally it!" I thought. After some time, listening to the album in Dolby Atmos and 360º Reality Audio became a bigger and bigger challenge for me. The thing is, you can't listen to this music "in the background" while relaxing. There are so many stimuli in this presentation that we are constantly on alert, so to speak. There is also something else. Mixes of this type change the way you perceive music because they are artistically a completely different event than a stereo album.

There is no "sound stage" anymore, even if it is an imaginary sound stage through the headphones, and there are many sounds around us, with vocals placed quite far away. I haven't found a single album that shows the voice close to me. It can of course be argued that this is how we perceive space during concerts - and it is true. Anyway, it was just like the "live" experience that I perceived with almost all albums. But it is also the case that when the most important element of a live event, i.e. the image, is absent, the sound has to be shaped differently. Otherwise, a large chunk of reality is simply missing.

▌ SUMMARY

I ended up listening to spatially encoded albums from time to time, but on a daily basis I use stereo files. The problem is also that almost all files of this type have a resolution of 16 bits and a sampling rate of 44.1 kHz. I only found one high resolution file. The point is that they require a high computing power of a smartphone and adding additional information to it can be troublesome. But for me, the problem is that the files are not hi-res ones.

⸜ Zoom microphone system used to record spatial sound • photo ZOOM

Will it lead to something in a long run? It is difficult to make reliable "predictions" in audio, I have already made several mistakes in the past. However, if I were to bet on something, I would say that both systems will stay with us for a longer time, perhaps permanently. Every now and then I read in the PRO trade press about the next "immersive" studios, that is equipped with Dolby Atmos systems, and there are more and more music albums encoded in this way. The key is universal access to this type of files thanks to streaming services.

For the perfectionist audio, it is more of a "leap to the side" than a progress, whatever the people involved in surround sound say about it. The problem is the resolution of the files, I’ve already talked about it, but also something else. While many albums are mixed specifically for this purpose, the great majority will only be "adjusted" by automatic systems using stereo files. This means that it will work sometimes, but often it will not. Therefore, I welcome the sound surrounding me through headphones with interest, but without much emotion. The "immersive" sound did not immerse me at all ... ■

WOJCIECH PACUŁA
Chief editor