The Sound Of 5.1: Aural Aesthetics

Discrete Channels And Complexity

Why is 5.1 a notable improvement over Dolby Stereo?

When most people think about digital sound, “improved dynamic range” is not the first issue that comes to mind. That honor would go to DSS’s multi-channel capabilities. “5.1” is now a part of everyday language, a fact that speaks not only to digital surround’s ubiquity in contemporary media but to DSS’s fundamental association with multi- channel sound.

Dolby Stereo ostensibly includes four channels—left, center, and right front plus mono surround—and, ignoring for the moment the LFE channel,
digital surround systems employ the same basic setup other than splitting the mono surround channel into stereo.
Digital surround sound, in contrast, offers completely discrete audio channels, meaning that the content in each one of its six channels is completely independent of what is in the others.
ability for literally more sounds to play at the same time.

If you get too many elements piled on top of one another, it becomes less dynamic. So sometimes I have a tendency to move stuff into the surrounds and have more all at once.
Steve Flick, Sound Designer (Spider-Man, Starship Troopers, Leatherheads)

Masking

When collapsed to one speaker or headphones, one sound of greater amplitude can cover another sound, creating a condition known as masking. . . . Variations of sound location, density, and volume in the surround channels can punctuate events on screen without the loss of intelligibility that might occur if the entire sound track was limited to the center speakers.

Complexity

the general level of complexity . . . has been steadily increasing over the eight decades since film sound was invented. . . . Seventy years ago, for instance, it would not be unusual for an entire film to need only fifteen to twenty sound effects. Today that number could be hundreds to thou- sands of times greater.
Walter Murch

Audiences ability to perceive sound

Humans can only pay attention to a limited amount of sounds at once
re-recording mixers know this and hence shape their soundtracks to focus audience attention on only two (or at most three) perceived aural objects at a time.
More sounds can be used if they are dissimilar

Terminator 2

Show extended freeway chase scene

Kinsey (2004)

Driving across the country interviewing people for a study

A montage sequence in Kinsey (2004) employs an even more complex mix than that of T2’s freeway chase. While the title character crisscrosses the country interviewing people for his sex study, the faces of his various interviewees appear onscreen over a U.S. map. Their voices also begin to mingle together and spread throughout the theater as they recount their stories. By the montage’s end, all five main sound channels are playing different sets of voices. These voices remain individually discernable, and audience members can choose if they want to focus on any particular voice to hear its story; alternately, they can simply listen to the mix as a whole, which continuously shifts focus among different voices. The result either way is a feeling of being overwhelmed by the number of different points of view present, an emotion made more powerful by the clear sense that this is not just “walla” sound but a vast collection of individual voices, all of whom have something worth saying.

Any sound, anywhere

Gladiator (2000)

Maximus walks from a small enclosed space out into the arena

As an example, a scene in Gladiator (2000) where Maximus (the film’s hero, played by Russell Crowe) walks from a small enclosed space out into a giant arena uses a gradual movement of sounds through all five channels. At the start of the scene, we hear the sounds of the small “waiting area” where Maximus is preparing to do battle; muffled sounds from outside also play in the background. As Maximus moves out to the arena, the camera moves with him and the soundtrack begins to shift. It gradually introduces the sounds of the arena (now heard without the “muffling” effect) to the front center, then the entire front, then gradually the entire theater (as the sounds of the original waiting area fade out in the rears). This design effectively conveys the overwhelming sensation of moving from a tiny underground tunnel to a gigantic stadium filled with cheering spectators, and it is made more effective by the way all the main channels are used together to precisely shape the move between these two spaces.

Contact

Rewatch opening scene in 5.1

Master and Commander: The Far Side of the World

places sounds all throughout the soundscape but carefully avoids putting effects in the surrounds that would draw attention away from the screen

Lifted (2006)

Play on Apple TV

The short Lifted (2006) uses careful placement of sounds around the multi-channel soundscape to indicate diegetic action beyond the edges of the frame. Here the abductor-in-training reacts to the offscreen sounds of an examiner making notes about his poor performance.

Throughout the piece, Rydstrom uses carefully panned sound effects to suggest both this (often offscreen) havoc and other diegetic sounds outside the borders of the frame, such as the trainee’s whining during a shot of his teacher making notes about his performance. One of the film’s funniest moments even relies on a surround effect: the abductor-in-training at last succeeds in directing the human out of the bedroom window—a success quickly marred by the fact that immediately after the body flies offscreen, a crash in the right surround channel reveals that it has hit a tree. This sound effect cues a cut to a wider shot revealing the body wedged in the tree’s branches. In this and other situations, Rydstrom carefully places sounds around the theater to heighten his film’s drama and/or comedy. But since all these sound effects have clearly indicated sources within the diegesis (even if those sources are not onscreen at the moment), the sound design never be- comes distracting or “too big” for the story.

Panning and Dialogue

The Kinsey example is a good one
Also the T1000 melting at the end of Terminator 2

An even better indication of how much digital surround’s discrete channel design has affected mixing practices is that dialogue is slowly being liberated to move around the theater like other elements of the soundtrack. One of the cardinal principles of multi-channel panning has been to keep dialogue front and center; filmmakers using magnetic stereo in the 1950s quickly learned this lesson, and the Dolby Stereo system appearing twenty years later technologically codified this aesthetic guideline. But now that the discrete channels of digital surround have made it technically possible to place dialogue elsewhere in the theater, some filmmakers are breaking with decades-long conventions to take advantage of this capability.

The Kinsey montage discussed earlier, for in- stance, gradually spreads the voices of its researchers’ interviewees around the whole soundscape, but it is clear in this case that no literal correspondence between image and sound is intended. In fact, while some of the voices in the montage are first heard in sync with onscreen faces, others are never associated with onscreen elements, and ultimately both types of voices spread into the surrounds even as some of the speakers’ faces remain onscreen.

The same fundamental principle is at play in the scene near the end of Terminator 2 where the T1000 (played by Robert Patrick) is melting in a pit of molten steel. Despite the T1000 remaining onscreen in a close shot, its screams whip around the surround channels.70 While this violates conventions of spatial matching between image and sound, it fits with the “spectacle” of the scene overall, recognizing that audiences are not expecting unadulterated realism out of this scene. Moreover, the T1000’s screams are, like the voices in the Kinsey montage, primarily effects rather than dialogue whose semantic meaning the audience is expected to decode.

Natural soundscape - Strange Days (1995)

Unnatural soundscape - The Ring (2003)

Both approaches - Spider-Man (2002)

the voice of his Green Goblin personality moves from speaker to speaker while his Osborn personality futilely tries to locate the Goblin.

Extensive Dialogue Panning - Cars (2006)

Full Frequency Channels

When SMPTE was developing the specifications for digital motion picture soundtracks, however, it recognized that the advantages of discrete channels would be partially lost if frequency limitations meant that the surround channels could only handle certain types of sounds. Hence SMPTE stipulated that every main channel be able to reproduce all audible frequencies.

The combination of full-range channels with a discrete channel configuration means not only that any sound can be placed in any channel, but that sounds can smoothly be panned from one channel to another. While brief stereo “fly-bys” across the front speakers have long been a staple of multi-channel soundtracks, digital surround sound represents the first commonplace system where sounds can move not just across the screen but all throughout the theater. Apocalypse Now famously panned helicopter sounds throughout the auditorium—but the full splendor of this multi-channel mix was only heard by viewers in a few showcase houses, as the standard 35mm Dolby Stereo prints of Apocalypse Now did not even include a surround channel.

Low-Frequency Effects

Phantom Menace Pod racer scene
In Lifted: LFE used for UFO rumble