Sound Advice: Audio in the Digital World

Today’s powerful computers, coupled with equally powerful software, allow us to do things on our desktop that were difficult or impossible just a few years ago. I have vivid memories of editing narration with tape and razor blades – and that wasn’t too far in the past. Today, with just a few clicks, I can do what took several minutes back then. Many video producers have replaced studios full of equipment with just one production computer. The trick is learning to harness all that new-found power and use it to sculpt gorgeous sound for your videos. Let’s look at some of the tools and learn to get the most from them.

Post It

Post-production is the process of combining all the elements of your video – from captured video and audio clips to graphics, narration, music and sound effects. All too often, the visual portion of the project gets the most attention, leaving little time (if any) to concentrate on audio section. That’s a shame, because today’s software makes it possible to produce a clean, professional soundtrack with a minimum of effort. Every traditional, standard audio tool and effect has its virtual counterpart already built into software, even my precious razor blades.

There are two potential environments in which to "post" your audio. The first is a dedicated audio program such as Sonic Foundry’s Sound Forge or Syntrillium’s Cool Edit. These packages provide full-featured recording, editing and effects processing. Multi-track platforms like Steinberg’s Cubase VST or Cakewalk’s Sonar allow for multiple channels of audio. With these programs, it’s simple to combine several voices, music segments and sound effects into a nicely blended finished product.

The second audio posting environment is your video editing software. For example, Adobe Premiere allows up to 99 audio tracks per project – more than enough for any video you’re likely to produce. The current version of Premiere has a nice set of audio tools including advanced trimming and volume controls and enough effects to satisfy most producers. Each environment has its strengths and weaknesses, so in the end you’ll probably use both types of software to finish a project.

Crank it Up!

Regardless of how you edit your audio, there are several essential effects for your production. The first is volume control. No rocket science here, just simple control over how loud or soft the audio is at a given time. When applied to voices or narration, the goal is to produce a solid, clean sound with plenty of volume. However, other audio elements such as background music and sound effects may need a lighter touch. Most programs also allow you to change the volume of a clip over time, raising or lowering the sound level to suit the moment. Many applications offer a neat feature called "rubber bands" or envelopes that lets you adjust the sound of a clip at any point on the timeline. With envelopes, you can make momentary changes in level or produce a gradual fade-in or fade-out. This is also a handy way to temporarily lower the volume of background music to make room for a voiceover.

Left or Right?

Another staple of audio mixing is the pan control. This adjustment is usually represented as a knob that turns to the left or right – moving the audio with it. Panning is very useful with sound effects. Let’s say that a phone rings in your video. The phone is located on the left side of the frame or even off-camera. By panning the phone ring sound effect to the left, the viewer can tell where the phone is located even if they can’t see it. This is common practice in film and television production. In addition to the virtual pan knob, you will also find envelopes available for controlling pan. In Premiere, the rubber band for panning is blue (the volume envelope is red) and can be adjusted with the same level of precision.

Even It Up

Next on the list of essential digital audio tools is the equalizer or tone control. Equalizers take many forms, from graphic to parametric, high-pass/low-pass to band-pass. Don’t let the jargon scare you; they all adjust the tone quality of your audio. Graphic and parametric equalizers contain several bands of control and cover the entire range of sound, from low to high frequencies. The others, considered filters, effect only one portion of the sound. Low-pass filters minimize the higher frequencies and are great for eliminating hiss. High-pass filters eliminate lower frequencies and are perfect for controlling wind noise and mechanical rumbles. Band-pass filters concentrate on one range of frequencies (a notch – usually somewhere in the middle) and either boost or cut the tone in that range. While most audio software offers surgical control of tone quality, video software is typically less exacting. In any case, your software will generally provide some choice of tone control along with adjustable frequencies and amount of boost or cut. Additionally, you can often stack filters to achieve a special sound, using individual controls for specific jobs.

A Little Louder Please

After volume and tone control, the next tool an audio engineer will typically use is a compressor/limiter. The job of this device is to minimize the difference between the loud and soft parts of your audio. Properly applied, the resulting sound will seem louder, clearer and punchier. Operating the hardware version of this audio gem is often more art than science. Your virtual compressor will probably be easier to use. This is a great tool to help minimize volume differences in multiple takes and will also help your voiceovers cut through a dense music bed.

The two primary settings you will deal with are threshold and ratio. Threshold is the point on the volume scale where the compressor starts to take effect. A lower threshold setting means the audio is compressed more often. With a higher threshold, only the louder portions will see the effect. Ratio is the amount of compression applied to the audio signal. A ratio of 1.5:1 will apply a gentle but effective compression. Set the ratio to 10:1 and you’ve turned the compressor into a limiter – flattening virtually all audio in sight. A careful balance between threshold and ratio will yield effective results and help make your audio sound more professional. This process also reduces the overall dynamic range of the audio, so be careful not to flatten your audio out too much.

Sweeten and Spice

So far, we’ve talked about digital tools that affect the volume and balance of our sound, but there is another category of effects that change our perception of where the sound takes place. The most familiar of these time-delay effects is reverberation or reverb. This effect simulates the acoustic environment of everything from a shower stall to a gymnasium. Reverb is often used to help match the sound of a voice recorded in a studio to those recorded during the video shoot.

Other popular time effects are echo and delay. Echo is just what you think. Imagine the sound of yelling "Hello" into a canyon. You’ll hear one primary echo followed by several diminishing echoes. Delay is basically the same, except with a single echo. Although these are considered special effects, they are useful tools and may come in handy on your next video.

The last of the time-domain effects are chorus and flanging. Chorusing happens when several very short delays combine with a touch of time shifting. It gets its name from its sound, which can seem like a single sound turning into a choir of sounds. Flanging is similar, but less subtle and often has a swooshy, jet-engine-fly-by sound. Listen to the middle section of the Eagles’ "Life In The Fast Lane" and you’ll hear a textbook example of flanging. Again, these are both special effects and should be used sparingly, but can also add unique sounds to your productions.

Finally

Take advantage of the powerful tools that are available to every computer videographer. Take the time to learn the strengths and weaknesses of each. Properly applied, these digital post-production tools can transform your audio from adequate to spectacular.

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