The EM Poll

Outer Limits

Nov 1, 2007 12:00 PM, By Brian Smithers

           

How to use good sound design in your music post-production work.

BONUS MATERIAL
Web Clips: Listen to audio clips that demonstrate special effect sounds created with pitch- and formant manipulation, reversing, editing, vocoders, subtractive synthesis, and more

The next time someone seems underwhelmed by your creative calling, put them in front of a movie with the sound turned down. Sure, visuals are impressive, but it takes sound to give them real substance. Without the dialog to weave a thread of meaning, viewers would rarely be able to follow a movie's complex plot. Without the music to steer and massage our emotions, most movies would never grab our hearts the way we want them to. And, of course, Foley brings us — consciously and subconsciously — just enough of the sounds of the characters' world to make it seem real without distracting us from the fantasy.

FIG. 1: Time- and pitch-manipulation effects such as Soundtrack Pro’s Vocal Transformer usually offer independent control over pitch and formant.

For pure visceral impact, however, it's the sound effects that matter. Nothing makes your heart feel as if it's about to leap out of your throat like the growl of a tyrannosaur or the shriek of an alien. The problem is that you can't always get a dinosaur into the studio — the good ones are booked solid, and their scale is totally unreasonable.

Good sound design brings to life creatures that never existed or that don't exist any longer. It takes ostensibly mundane sounds and makes them sound as threatening (or tragic or exciting) as the onscreen action feels. In this article, we'll explore some techniques for creating sounds that are supernatural or surreal. These methods are used in both film and game production. Although the two fields differ greatly in the way sounds are implemented, the characteristics of a good sound are essentially the same for both.

Familiarity Breathes

Although it's natural to be fearful — or at least a bit apprehensive — at the sight of a space alien or werewolf, filmmakers understand that evoking real terror requires something the viewer recognizes as dangerous. Thus, most movie creatures have fangs, claws, stingers, pincers, or something familiar enough to scare us immediately. It's important that creature sounds take advantage of this familiarity, too. Although a sound you've never heard before might alarm you, a sound that reminds you of a lion's roar will raise the hair on the back of your neck before you even start to deal with it on a rational level.

The flip side of this familiarity axiom is that if the listener hears that the sound of an alien is actually a lion's roar, the illusion is blown. So although it's good practice to build supernatural sounds from natural sounds, it's essential to fool the listener into feeling the familiarity without recognizing the familiarity. This is accomplished by breaking the original sound's context.

Both multitrack and 2-track audio editors offer an almost unlimited variety of tools for disconnecting a recorded sound from its original context. Cut up a few lines of dialog and shuffle the syllables, and you can create a dead language. Reverse the same lines to create the classic dream sequence. Notable sci-fi villains like Dr. Who's Daleks or the original Battlestar Galactica's Cylons were created by using ordinary dialog as the modulator input on a vocoder. Each of these examples plays on our ability to accept and process the familiar aspects of a human voice while simultaneously pulling us out of our comfort zone by processing that voice in unnatural ways.

Let's start with a bit of alien dialog. Although it's tough to imagine that when we meet visitors from another planet they will speak English, it's important that moviegoers be able to recognize film aliens' utterances as language. Thus, most movie alien sounds begin as normal human dialog.

Hearing Voices

Web Clip 1 is a short conversation between aliens from two separate planets. The raspy voice is my friend Andy trying to coax his two-year-old daughter Sachiko to the microphone; the second voice is hers. I imported Andy's lines into Apple Soundtrack Pro, which is part of the Final Cut Studio 2 suite.

FIG. 2: Sonar’s V-Vocal offers a graphical environment for altering pitch, timing, volume, and formant.

Reversing the file made the language unintelligible while maintaining a sense of timing and intonation that is immediately recognizable as conversation. The challenge with reverse dialog is that too many syllables end up as crescendos, giving away the technique. To avoid this, I deleted some of the suspect words, simultaneously rearranging words to create a different flow. In some cases, I unreversed consonants and then grafted them onto the beginning of certain words.

The voice still sounded too human, so I inserted Soundtrack's Vocal Transformer effect and experimented (see Fig. 1). Andy has a nice, deep voice, so I had plenty of flexibility. Like most current pitch plug-ins, Vocal Transformer offers independent control of pitch and formant, allowing you to reduce the chipmunk effect when tuning a vocal. In this case, I embraced the rodents by cranking the formant control up several semitones. It immediately gave the impression of having moved Andy's larynx up to his forehead without actually reducing him to a chipmunk.

To balance the nasal quality of the voice, I lowered the pitch by about an octave and a half. The result is a creature voice with weight befitting a large and powerful body, timbre suggesting an alien vocal apparatus, and phrasing that evokes ordinary conversation. Applying the same processing to dialog with more emotional range would give a result that tracked the actor's performance well.

The other creature voice was somewhat more challenging due to the airiness of Sachiko's voice. I tried several different pitch-shift plug-ins within Digidesign Pro Tools, Cakewalk Sonar, Apple Logic, and Soundtrack before settling on Sonar's V-Vocal. V-Vocal's graphic time manipulation allowed complete freedom over Sachiko's phrasing (see Fig. 2). I stretched and squeezed syllables, even individual phonemes, to shape each line as needed.

I shifted her pitch down about an octave and her formant a little more than half to obfuscate her gender and age. The result retains her innocence, suggesting a naive, daydreaming sort of character. Occasionally, the algorithm struggled to track the little hesitations and chirps that are typical of a two-year-old's voice, so after bouncing the processed vocal to a new clip, I selectively edited out those sounds, leaving some in for effect. Sachiko's native accent is Japanese, and she created some wonderful nonsense phrases, so I had great freedom in editing together the sort of phrases I needed.

As I Live and Seethe

Some of my favorite science-fiction shows imagine organic technology, the sort of thing where a space vehicle is to some degree a living thing. Despite the fact that sound does not travel through the vacuum of space, the spaceships in virtually all movies, games, and television shows are audible to the audience. Most of us choose to overlook the paradox and accept the aural cues as indications of an object's size, speed, position, and even purpose. Hearing the sound of a living, breathing, menacing space vessel in my head, I turned to the vocoder, a time-honored device for blending human and electronic sounds.

FIG. 3: Native Instruments Vokator is a powerful sound-design tool built around a flexible vocoder architecture.

I created an audio track for my voice and an instrument track for Native Instruments Vokator (see Fig. 3). I used a bus to route the output of the vocal track to the input of the Vokator track and then set Vokator to use that input to modulate its internal synthesizer. Because the vocal track would not be heard directly, I grabbed a ten-dollar mic and started tweaking the sound.

One of Vokator's better features is its ability to morph between settings in response to CC 1 messages, so I created two timbres — one for the ship's approach and another for its departure — and used my keyboard's mod wheel to glide between them as the ship passed by. It took a good deal of fine-tuning to get the right balance of pitched to unpitched sounds in each timbre in order to make the ship sound more mechanical and less musical.

To give the alien vessel as much subliminal angst as possible, I recorded several tortured cries. Over these sad syllables I played random 3-note combinations, eventually settling (fittingly, some would say) on a minor triad. I used a fade-out to smooth the sound of the ship flying away and a fade-in to obscure the initial consonant, lest the illusion be compromised. With a bit of practice, I was able to get the Doppler shift about right with my keyboard's pitch wheel, but I still did some hand tweaking. With the addition of a small amount of reverb, Web Clip 2 was born.

BONUS MATERIAL
Web Clips: Listen to audio clips that demonstrate special effect sounds created with pitch- and formant manipulation, reversing, editing, vocoders, subtractive synthesis, and more