6 Sound Effect Restoration Tips

2014/02/19

6 Sound Effect Restoration Tips Hero

Earlier I wrote about an update to a popular audio restoration app, iZotope’s RX3. That software has the powerful ability to recover damaged audio and restore precious clips that would be useless otherwise.

Clicks, crackle, hum, and noise are all irritating problems for sound pros. Why? They often mean the difference between using the audio, or deleting it.

This is why restoration software like RX and its peers seem almost miraculous. It gets dialogue editors, mastering techs, and post crew out of tight spots. Part of this is learning the tools: the settings, switches, and plug-ins that do the job best. These are essential, but ultimately they can be figured out with practice.

Today I’d like to share something different: the perspective needed when restoring audio. These are ideas that are helpful when beginning restoration. They’re not about settings. They’re more about cultivating an approach to denoising that will save you work, time, and help you transform sound effects you’re proud of.

Looking for concrete tech tips? I’ll share specific iZotope RX suggestions in an upcoming article.

  1. Restoration While Recording
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    Imagine you’re recording tools in a machine shop. You’ve cleared out the staff, and have your props lined up. Your gear is perfectly aligned. Then you notice buzz on the track. It’s definitely coming from the environment. Fluorescent lights? Perhaps a transformer is nearby? You can’t pinpoint the source. It’s slight. The shoot is ready to begin. People are waiting. You have a killer hum removal plug-in at the studio. Surely you should proceed, and just fix it in post?

    Well, you may be able to, it’s true. However, “restoring audio while field recording” is a bit of a trap. Denoising tools are so powerful that they can seem like a band-aid for any issue. It’s easy to assume you’re invulnerable to hum and noisy preamps on location because your software will save you later.

    The trouble is that this approach directly affects your craft as a field recordist. You may gradually slip into the practice of recording weaker tracks that accommodate for tools not there at the time. It’s often done unconsciously.

    The most important thing is to record a good source track. If your location field recordings begin as the weak link, that will only ripple further down the chain of editing, mastering, curating, and sharing.

    Forget about your restoration plug-ins when you’re recording.

  3. “Kill Your Darlings”
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    American author William Faulkner famously said:

    In writing, you must kill your darlings.

    The idea was that your work improves by trimming away your favourite creations that aren’t quite up to scratch.

    Field recording is a pretty cool craft. Sometimes the people we work with, or the event itself can lend more meaning to the tracks than sound alone. Stealth missions are exciting. Group recording is fun. It’s easy to become attached to the tracks we capture.

    The problem? Sometimes this clouds our judgement of what is a superior sound effect, and one that is merely “okay.” This is what I meant when I wrote that a field recordist needs a built-in, shock-proof shit detector. What does this mean for audio restoration?

    That article mentioned the temptation to keep weaker clips that you feel attached to. This happens when restoring audio, too. It’s common to approve a sound effect with just a bit of noise or buzz because the sound is cool, or we enjoyed recording it.

    Instead, delete it. Don’t waste time deonising common files. Trash them, and record with more appropriate levels or equipment. In my experience, struggling denoising or fixing a common file is not worth the time or frustration. It’s quicker to just record it again. Your results will improve. You’ll feel more confident with your sound library. Isn’t that better than knowing in the back of your mind that your entire footstep collection is only 80% perfected because there’s a trace of noise your mastering was forced to keep?

    Instead, focus on using audio restoration only for the most significant or irreplaceable sound effects. A new file that you’re 110% excited about is far better than a weak recording improved to 80%.

    Kill your darlings. Repair only exceptional files.

  5. A New Type of Editing
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    I remember my first time trying audio restoration. I had plenty of experience editing sound effects, and mastering sound libraries. I sat down, expecting that it would be just like using any other plug-in. I quickly learned otherwise.

    Audio restoration may seem similar. It can be invoked just like other plug-ins we have. When using the native RX app, it can seem just like the editing in other DAW apps. It’s non-linear. We can scrub and copy and paste. The truth is that while audio restoration may take the same shape as conventional editing, it requires vastly different skills.

    Conventional editing requires a good eye to spot synchronization, the ability to chop and blend clips, and arrange many sounds to work well together. We’ve built those skills over years. Unfortunately, they won’t apply during audio restoration.

    Editing skills are global. Audio restoration requires a more detailed focus. You’ll need the ability to discern the most minute changes in audio. You’ll need to listen more keenly. You’re focusing not on how clips work together, or with picture. It doesn’t matter if a clip is a good creative fit or not. Instead, you’re listening to the same sound effect repeatedly with intense detail.

    Dialogue editors often listen to and analyze a single track repeatedly, especially when trying to fit ADR. They will have an edge here. But, since most of us are sound effects recordists, we’ll need different skills.

    This means that you’ll need to shift your perspective when fixing audio. Your five years of experience won’t produce the same quality of results denoising as it would when editing post. Why?

    Conventional sound fx editing largely involves context. Audio restoration is solely about the content itself.

    This won’t set you too far back. Just remember to shift your approach when restoring sound effects.

  7. Spotting Your Own Errors
  8. 6 Sound Effect Restoration Tips 4

    Everyone’s heard the story about the child that hides under blankets and thinks because he can’t see others, they can’t see him. It’s an idea from psychology called object permanence. What could this possibly have to do with audio restoration?

    Well, restoration is never invisible. Because audio restoration is so sophisticated, results are often deceptive. Everyone knows that no skill is mastered the first day you begin. This has an important side effect when restoring audio: your first attempts may fail, and you may not know it. You may not be able to detect the minute changes that advanced sound editors will. Why not?

    Some of it is training your ear. It also helps to know the shortcomings of audio restoration apps. This is often just a matter of time and experience. The problem is that inexperienced mastering techs won’t know that right away. They may not be able to spot the subtle thumps that remain after aggressive declicking. It’s easy to miss the faint slushiness of denoising aliasing hiding behind transients.

    The larger concern is that anyone with restoration experience can spot denoising a mile away. That’s true if the denoising has left obvious artifacts, of course. However, it’s also true even when denoising has been done “properly.” No sound that has been affected by restoration will ever sound “normal.” It will always have a slight cast to it. For example, the lack of noise may be just obvious enough to set off a “glitch in the Matrix” sense to listeners. It just won’t feel right.

    The result? It means you may not be able to notice errors in your own work at first. It also means that even what you consider is your best work may be rejected by more experienced pros. Finally, it’s natural to return to your work years later and spot ways to improve it. However, audio restoration can be a one-way street. It’s hard to adjust files after they’ve been processed once.

    I don’t mention this to discourage you in the slightest. It’s important that you do begin. After all, if you don’t start, your audio restoration skills won’t ever improve. Practice on less important files. Make backups. Ask colleagues for feedback. Just consider that your first attempts may need touching up years down the road after your skills improve, or better technology emerges.

    And what about that technology? It’s natural to assume restoration tools will fix problems the first time, every time. That’s how they’re marketed to us, after all. Like any other technology, it has limits. It’s best not to take any tool for granted. Consider thinking about audio restoration differently. Remember to turn a critical eye toward the tools you use, and your own work, too.

    Be aware that audio restoration has an unforgiving learning curve. Just don’t let that stop you from trying. You’ll notice your results improve dramatically with only a bit of focused effort, and a discerning ear.

  9. Working In Passes
  10. F-35 Integrated Test Force

    Audio restoration requires working in “passes.” To get the job done, you will listen to a single clip repeatedly: testing, applying, undoing, and revising. You also will apply one fix, then follow with another. For example, you may strip out the hum, then later work on the noise.

    This creates two side effects:

    1. Restoration affects audio incrementally. Your work is always built upon your last attempts. It’s important to make sure that your current work is exceptional before going to the next stage. Make sure your hum extraction is the best possible before moving to denoising, decrackling, or whatever. Otherwise your results will be built on an increasingly shaky foundation.
    2. Working in passes often results in losing perspective. You’ll be wrestling with problem audio in waves. It’s common to become so deeply focused in small, repeated changes that you get wrapped up in a spiral of work. You may find you’re “making deals with yourself” to accept small imperfections that increase with each pass. Perhaps you’re so deeply focused on the noise behind a single transient that you’ve lost sight of emotional impact of the entire clip.

     

    How do you avoid this? It helps to back out and regain perspective. I reference the original file before I commit my work. I’ll apply all my restoration steps, one by one, usually over a long period of time. I’ll end up with a track I’m happy with. Just to be sure, I undo all of them, step by step. That helps me listen to each improvement, from one to the next, more quickly and objectively.

    It gives me perspective, and pulls me out of the deep focus I had while struggling with a file during the last half hour. If I’m satisfied, I simply redo the changes back to the final result, and commit the file.

    You will find your own tricks. Sometimes it’s as simple as taking a break and returning to your work five minutes later.

    Either way, back out, and use perspective before committing your work.

  11. There Is No Silver Bullet
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    The biggest challenge when restoring audio? You’re more likely to damage it than improve it.

    Wait. Isn’t restoration supposed to fix your audio? It’s true. There are two issues, though.

    1. Audio restoration apps are tricky to use properly, especially for sound effects work.
    2. Often junior mastering techs will destroy audio irreversibly and have no idea. We saw this in “Spotting Your Own Errors,” above.

     

    You’re working with damaged audio. It may have been your slip up. It could be a mistake by a production sound mixer you’ve never met. Perhaps it is something beyond your control. Whatever the reason, it means you’re starting with poor audio to begin with. What’s the point?

    Expecting perfection from damaged audio is inviting frustration. When we begin restoring a clip, problem sounds will initially consume most of the focus for listeners. For example, maybe hum is dominating the clip, or the fx are soaked in noise and hiss. You’ll notice those errors more than the sound effect itself.

    The goal of audio restoration is to swing that focus in the favour of the sound effect, instead of the problem. To do that, we need to diminish the problems to the point where the sound effect takes up at least 51% of the focus (hopefully much more). The most important point, though, is that this will never be greater than 99%. How come?

    Restoring damaged audio to perfection is hard. The inherent nature of the audio repair technology is that it will always be a bit of a cheat. Because of this, it’s helpful to remember that restoring audio is always working from behind. Why?

    Well, it’s a challenging skill to learn. You’re working with damaged audio, and are trying to make it become something it’s not: perfect field recordings. In a way, it’s like trying to rebuild a smashed glass. Restoration apps can’t bring damaged audio back from the dead. They can get close. Sometimes quite close, even to 99%. But that broken glass won’t be exactly as it was.

    I don’t mean that it’s a bad idea to use it. You definitely should! Restoration produces amazing results.

    However, it’s helpful to realize that repairing audio always involves compromise. Yes, results can be impressive, even exceptional. Just consider the idea that audio restoration apps, even at their best, aren’t a “silver bullet” that solves any issue. That isn’t a de-hum or de-noise module. Instead, the silver bullet is you. That’s the skill, judgement, and creativity you use when you are gathering sound effects in the field.

A New Tool

It’s true. Audio restoration is challenging. It requires a good ear, patience, and a fine knowledge of restoration tools.

You will master those tools over time. You will sharpen your skills, and judge every clip with a critical ear. That knowledge will produce excellent clips. Amplify them by wrapping them in a discerning perspective, too.

Next week I’ll share some specific audio restoration tricks.





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