Edit Your Audio, Too

If you've read the pages of Videomaker for a while--or maybe even if you haven't--you probably have a pretty good idea what video editing is. All you need are the right tools and equipment, some know-how and a good set of eyeballs. Pretty simple stuff, when you get right down to it.

But have you thought much about what it takes to make a good-sounding video? As it turns out, the requirements are basically the same. Good soundtracks require that you have access to the right tools, have an audio-savvy brain and a good set of ears. Thankfully, videographers at any experience level and budget can get all three of these without a huge investment in time or money.

What follows are a half-dozen basic guidelines for effective audio editing. These are designed to lay a foundation of knowledge that will serve you well on your next video. Until then, listen up!

Guideline #1: Keep Your Goal in Sight
When it comes to audio editing, videographers will have different goals for the many different types of scenes they're working with. In one part of a video, you may be using music or sound effects to enhance a certain mood. In another section, adding sounds may be the key to helping the audience suspend their disbelief of some on-screen illusion. Every audio goal is important, and each requires a slightly different approach.

If your goal is to enhance a certain mood with sound or music, subtlety is the key. The chirp of birds, the crackle of a fire, the patter of a gentle rain and other such mood sounds can add immensely to a scene if used with subtlety.

Keep in mind that these are background sounds and should never compete with dialog or other sounds. Before recording, do a test pass for each scene. Raise the level of the background sounds until they start to become obvious, then back them down a bit.

Using background sounds to sell an illusion also requires subtlety. If you want an audience to believe your video's hero is tottering on a window ledge atop a 120-story building, a little wind and distant traffic noise would come in handy. Push the level of these elements too far, though, and your audience won't buy it. They may even laugh.

But there are some sound effects that usually don't require much in the way of subtlety. Gunshots, explosions, sirens and helicopters should be loud in the mix to give them as much power as possible. If it's realism you're after, choose your sound effects with care. Sounds that are too dramatic for a given scene can come across as corny or overblown.

CD libraries are great sources of sound effects and background ambiences. If you can't afford to buy these CDs, try recording your own effects. Your camcorder is an able audio recorder, and you can use it as such to capture effects. When it comes to cooking up your own sounds, the only rule is that there are no rules. Creativity is the key to effective home-brew effects.

Guideline #2: Continuity is King
Every place you shoot has its own very distinct aural signature, made up largely of ambient noises and reverberation (or the lack thereof). You may not notice this acoustic signature consciously, but your brain learns much about its environment from these subtle aural cues. Controlling and "faking" this acoustic signature is the key to maintaining aural continuity from one shot to the next.

Why do we need to worry about continuity at all? Because scenes shot in two different locations will have distinctly different ambiences. Cut two such scenes together, and your viewers will notice the abrupt aural shift. The edit may look fine, but the lack of continuity in the audio will draw unwanted attention to the edit.

The best way to maintain aural continuity involves a two-step process that starts on the shoot. Before you leave a given location, let your camcorder record a few minutes of "nat sound" when nothing noisy is happening. Nat sound is the natural ambience of a room or outdoor location, and it's far from silent. The hum of an air conditioner, the babble of voices in the next room, the distant roar of a freeway--all of these contribute to the unique personality of that location. By capturing some of this ambiance, you can apply it in post-production to maintain continuity.

Mixing some of this ambiance into your audio where appropriate will lend a consistency to the soundtrack. Almost like aural "wallpaper," nat sound smoothes over what would otherwise be bumpy, uneven audio. Because fidelity and synchronization aren't important in nat sound, you can dump it down to a regular audiocassette for playback. Trickle a little into your soundtrack, and the results are amazing.

Here's an example of the use of nat sound in preserving aural continuity. At a local diner, Paula shot a dramatic scene that captured a heated discussion between a man and woman. At one point, with the camera catching the man's reaction, the woman drops a bombshell--her mother is coming to live with them. The actress delivered her line smoothly, and the man's reaction was perfect. Paula was happy with the take, and began to tear down her equipment. As she rolled up her mike cables, she let the camcorder record about five minutes of the natural sound of the diner. Later, she would be very glad she did.

Upon reviewing the footage, Paula discovered that a loud cough from just off-camera ruined the actress' key line. There was no time for a re-shoot at the diner, so Paula had the actress come to her house to record the line again. Paula miked the actress with the same lavalier mike, being careful to position it in roughly the same spot. After three tries, Paula got a keeper take.

Dubbed straight into the scene, the new line would sound awful. The background bustle of the diner would disappear for the duration of the edit, replaced by the stuffy quietness of a living room. To make the edit invisible, Paula adds in some of the nat sound of the diner from an audiocassette. After two or three tries, Paula gets the nat sound level set to match the other shots. The result is a seamless edit, with no change in background ambiance. The scene is saved.

Guideline #3: Set Record Levels Carefully
Every electronic circuit--be it camcorder record head, audio mixer input or home theater amplifier--has a signal level it performs best at. Feed a circuit a signal that's much lower than optimum, and unwanted noise begins to threaten the integrity of the signal. Give the circuit too strong a signal, and abrasive, harsh overload distortion is the result.

Every place you can control signal levels, you should. If your record VCR has automatic or manual record levels, use the latter and set levels yourself. No automatic circuit can do a consistently good job setting levels; with practice, you can.

The main goal in setting proper signal levels for recording or dubbing is always the same: keep levels as high as possible without distortion. Peaks (occasional loud sounds) have a greater effect on where we set levels than do "average" sounds. Watching your meters closely for a minute or two should give you a good idea how severe any signal peaks are. Are you recording the consistent rush of a waterfall, or the drone of an uninspired narrator? If so, peaks will be relatively mild and you can set your average levels quite high. Program audio with occasional loud sounds will require you to set your average level much lower to keep peaks from distorting.

Most level meters show optimum signal level at "0dB." Meter readings below optimum fall into negative numbers (-12dB, for example), while higher values go positive (e.g., +3dB). Analog circuits rarely distort if signals push a little beyond 0dB--most have "headroom" to accommodate the occasional signal peak. Digital systems, on the other hand, usually distort severely the instant a signal passes 0dB.

Here are some guidelines for setting input levels on various types of audio post-production equipment:

• Digital audio recorder (Hi8 PCM, DV, nonlinear editing system) Think of the 0dB level as a "brick wall" that will destroy your audio signal if you push into it. Set levels so peaks hit at about -2dB or -3dB.

• VHS-family linear track Though this is an analog audio format, its relatively poor performance gives it very little headroom. Don't let peaks push past about +3dB.

• 8mm-family AFM audio The AFM track has a generous (read forgiving) amount of headroom. On most systems, peaks will stay clean upwards of +6dB.

• VHS and S-VHS hi-fi Thanks to an audio compression system, hi-fi audio has headroom galore. I've seen average levels running at +10dB, with peaks considerably higher than that. With most hi-fi VCRs, you can light all the red LEDs and still not have distortion. To be safe, though, keep peaks below +10dB.

• Analog signal processor (i.e. compressor, EQ) Most analog processors have good headroom, handling peaks of +10dB with ease. In general, though, try to keep average levels around 0dB with peaks around +6dB.

• Digital signal processor (i.e. reverb, delay unit) Like a digital recorder, most digital processors clip severely above 0dB. You can feed conservative levels to these processors and still enjoy excellent sound quality. Keep peaks between -3dB and -6dB.
  

Guideline #4: Use Audio Processors
As a videographer, you probably have a grasp on the ins and outs of color correctors, special effects generators and other video toys. But did you know that there are countless audio processors available, each as useful to good videography as any video processor? Knowing how to apply these processors in post-production can make a huge difference in the quality of your soundtracks.

Here's a quick run-down of the most common audio processors, and how they can help the sound of your videos.

• Equalizer All sounds cover a certain range of frequencies. When a sound is lacking (or is too strong) in one frequency area, it doesn't sound quite right. Improper miking usually results in such out-of-balance sounds, and an EQ can go a long way towards fixing the problem.

  An EQ lets you boost or cut specific frequency ranges. If a mike sounds dull and muddy, removing some low-mids can clean up the sound. If a speaker sat too far from his mike, an EQ can bring up the bass to restore the missing warmth. Most audio mixers have simple EQ built-in, which is adequate for many needs. When you need more control, however, a stand-alone EQ is the best solution.

• Compressor/Limiter Instead of altering frequency balance like an EQ, a compressor/limiter affects the level of a signal. Compression involves reducing the volume of loud sounds, while bringing up the level of quiet sounds. This makes your audio much more consistent in level, and gives it a louder, more "in-your-face" quality. TV ads often use extreme compression, making them sound much louder than the show they're interrupting. Limiting performs more severe processing than compression, but only on the loudest peaks. Limiting is less noticeable to the ear, and is useful for keeping loud sounds from distorting during recording.

  Most "dynamics processors" will perform compression or limiting (some do both at the same time), and most are stereo units. Investing a few hundred dollars in a compressor/limiter--and learning to use it properly--will go a long way toward improving the quality of your soundtrack.

• Reverb/delay unit This type of digital processor adds the most deliberate "effect" to your sound by creating something that wasn't originally part of the audio. Reverb processors simulate the smooth decay of sound you hear in a room; delay processors create a repetitive "Hello... hello... hello..." echo effect.

  Reverb and delay effects can be useful in creating a disorienting, unreal sound. This type of effect could really enhance a dream sequence or similar scene. Don't go overboard with this type of processing--a little bit tends to go a long way.

  Artificial reverb can be an aid in maintaining continuity, as you can add the sound of a given room onto an otherwise "dry" recording. Note that it's quite hard to simulate a natural space exactly, and no reverb processor will add in the other noises that give a location its unique character. In most cases, you're still better off recording some natural sound on the shoot.
  

Guideline #5: Stay in Sync
Synchronization of sound and video quickly becomes an issue when editing. The important thing is to make a distinction between those audio elements that must stay in absolute sync with the video and those that can run "wild." Unless you have an audio recorder that will chase time code (assuming you have a time-code system), your best bet is to keep synchronized elements on videotape. The audio won't slip out of sync or wiggle around in pitch if it stays securely on tape.

Elements that don't require sync can come from any number of different playback sources during an edit. You can route CD players, cassette decks, MiniDisc players, VCRs and computers into an audio mixer to blend sounds on the fly. To get things in rough sync, look for a specific on-screen action to cue you where to start your audio sources. ("If I start the CD just as the car door slams, the music fades out at the perfect time.") Because most audio sources play back at a reliable speed, you'll get consistent results until your edit is complete. In the off chance you'll need to re-edit a scene, make a written note of where you started each audio element.

Audio elements that require sync include:

• Any on-screen dialogue (mouth visible), and

• Sharp sounds that coincide with on-screen action.

Audio elements that don't require sync include:

• Off-camera dialogue.

• Talent talking at a great distance (wide shot), or with mouth not visible.

• Background music.

• Background ambience (natural sound).

• Sustained sound effect (earthquake rumble, siren).

Some videographers mix their non-synced elements together onto one tape, often called an audio "submaster" or "submix." This is more convenient than trying to start numerous different audio sources at the same time, but it does have one disadvantage--you can't adjust the relative level of sounds once you mix them together.

Guideline #6: Know Your Gear
Our last guideline is almost obvious in its simplicity, but many folks overlook it. In simple terms, know your equipment inside and out. Know the capabilities of your audio mixer. Know which tracks will and won't dub on your VCR. Have a good grasp on the signals levels that your various equipment will handle.

The better you know your equipment, the more smoothly each edit session will go. More importantly, your finished product will look and sound much better. Learning all about your equipment may require reading the manuals (gasp!), but you'll never regret the time you spent exploring your gear.

Remember: you can never know too much about your equipment.