Fix it in post. These words have the power to give editors ulcers, and yet they flow off the tongue so easily, they've become a clichè. Of course, if time and money are not a concern, you can fix just about everything in post. For the more budget-conscious (that's you and me), it pays to know what you can and can't fix and how much trouble you'll cause. The good news is that, with modern sound -software, plug-ins and a little time, you can repair all but the most serious audio gaffes.
Making the Call
Many of us are lone-wolf video producers. We wear many hats throughout the production process: writer, producer, shooter, editor, janitor and even therapist. You know the drill. Somewhere in the midst of a shoot, you must decide what, if anything, can be repaired afterward in the edit suite. Knowing your options is the key. Here's a typical scenario: you're shooting a corporate video, and the CEO insists on being the pitchman. That would be fine if he could memorize his lines or at least read off a teleprompter, but, alas, he can't. In fact, he continues to trip on one simple section of the script (that he wrote), and you just can't get him past it. The planned shot for this little scene was a slow continuous push on the CEO for the entire paragraph of text. Now, you're on take #27, and it's after 4 o'clock. You need a way out.
This is a visual example, but my guess is that you're already thinking of options. Perhaps you could shoot it in two segments, covering the edit with B roll or a flash. Maybe the entire open is B roll until the end, allowing the CEO on screen for the wrap-up. Another option is shooting as if there were two cameras, cutting to the alternate angle in post, covering the edit point. No one would know, and the CEO could look like a genius. Let's apply some of that same creative thinking to the audio in your project.
You can solve many audio problems quickly with some simple but effective techniques. Back in olden times, audio processing required a studio full of expensive gear. Today, it's all just software and a handful of plug-ins - many of which are free. After the shoot, you get back to edit and discover the audio has an annoying 60Hz hum. A ground loop between your camera and some other audio or video gear likely caused the problem but, right now, it doesn't matter how it happened - you just have to fix it. Dig through your audio options and find a notch or parametric filter. With a notch filter, you tune to a specific frequency - in this case, 60Hz - and control how much the filter removes. It can be that easy, unless you have some very nasty hum or there are other frequencies involved. In that case, try a parametric filter. Every parametric is different, but they all share some common features. A parametric filter allows you to select the frequency you want to work on, how wide a band the filter affects and how deep you want to cut (or boost) that frequency. Many parametrics have three or more bands, each tunable for different ranges. This makes it easier to do your audio surgery with just one plug-in. Don't be afraid to play with the settings. There's always the Undo button. With the level of quality and control offered by today's audio plug-ins, it may be tempting to go a little crazy with the settings. Dial in just enough to do the job, no more. Your ears and your viewers will thank you later.
Sometimes, all you need is some basic volume control. Most NLEs allow the editor to make volume adjustments to each track and each clip within the track. In addition, it's also possible to draw volume adjustments throughout the track. With this feature, you can create fast or slow fades, tame a single loud sound or boost a section of dialog to match other clips. This requires the use of keyframes on the audio timeline. By setting keyframes at critical points, it's fairly easy to raise and lower the track volume as needed, whether for an instant or a long period of time.
Set for Stun
Background noise is messier. If your background noise is the type that changes over time - like traffic or nature sounds - I'm afraid you're on your own. However, if the background noise is constant, it's possible to minimize or eliminate it entirely. These are usually mechanical sounds like air conditioners or refrigerators, but it might simply be excessive noise from an audio mixer. For this type of fix, it's time to move your track into a dedicated audio editor. Many digital audio workstations - or DAWs - supply noise reduction as standard equipment. If your DAW doesn't offer this convenience, check out noise reduction plug-ins from Sony and Izotope. It could be an expensive option, but likely more economical than a reshoot.
Using Adobe Audition as an example, let's remove some background noise. On the surface, Audition's noise-reduction algorithm isn't all that complicated - sample the noise, select the whole track and hit the OK button. But once you get into it, there are many variables, and some combinations of those variables are completely unusable. Start by identifying a section of the audio that is noise only. One second or more is ideal but less will work. Highlight the section, open the Effects option, find Restoration and select Noise Reduction. By clicking the Capture Profile button, you're telling the software that the selection is noise. Soon, you'll see a graph of the noise. Using the default settings, click the Select Entire File button and then OK. The software will do some serious number crunching to extract the noise you defined. Once it's finished, play the track and listen closely. If you hear clean, normal audio minus the noise, you're done. If not, undo the noise reduction, carefully select some noise and try different settings in the Noise Reduction dialog. With some trial and error and a little patience, you can remove most constant background noises. Remember, this used to be impossible. No complaining if it takes a couple of tries to get it right.
As with all new skills, audio cleaning will take some practice. Try each of the techniques we've described. If your audio software isn't up to the task, investigate an upgrade or the possibility of extending its power through plug-ins. There are mountains of free and almost-free VST plug-ins on the internet, and most audio platforms support them. Take a look. Or course, it's best to get the audio right from the beginning. But if you find yourself in a pinch and know all your options, you really can fix it in post.
Contributing Editor Hal Robertson is a digital media producer and technology consultant.
Sidebar: Face the Music
Let's be real: sometimes you can't fix it in post. Then you have two options: mask it or ignore it. You might be able to cover some of your audio weirdness with some simple music. The difference is enough to distract the listener, and it could save an edit. I know it sounds cheap, but it's done all the time. Your final option is simply to embrace the flaws. Clean them the best you can, but, at the end of the day, live with them. You can tell everyone it lends honesty to the piece!