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Another technique that works well in the Frequency Space Editing environment is to use the Repair Transient command. Radeke demonstrated this with a preset Adobe demo file of a string quartet recording marred by someone coughing in the audience.
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| One cough has been deleted, while another is highlighted. |
"If you're a Photoshop user, you know what the Healing Brush is. The way I present this is that it's the Healing Brush for audio," Radeke said. "It does the same kind of thing -- it looks at the pixels you've defined and creates a blend. It allows you to distinguish between the vibrato of the violins, which are still there, but pulls out the information of the coughs as a transient event."
Audition's suite of Restoration tools is also very useful for Frequency Space Editing, as Radeke showed. He loaded a voice recording file that had several problems, including intermitment high-pitched sounds, ambient background noise and a constant low-level hum. In the spectral view, the high-pitched sounds were easily identifiable, and he zoomed in to select one of them. Then he opened the Noise Reduction filter [Effects>Restoration>Noise Reduction], and clicked Capture Profile, which scanned the selected audio to create a noise reduction profile. Finally, he selected the entire file, clicked OK, and zoomed back out. Most of the bad high-pitched frequencies were gone throughout the file, and the operation could be repeated as needed.
Radeke used the same procedure to get rid of the ambient noise, highlighting a small area of it to create a noise profile and then selecting the entire file to remove most of the noise. For demo purposes, he performed this operation just once. "But you might want to take a couple passes at it," he said. "People think you can only use noise reduction once or you're going to start destroying your file. But with the spectral view and the noise reduction tools we have, we can really have a lot of surgical precision."
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| Noise profile of hum has been captured from horizontal band at far left, and the entire file has now been selected to remove the hum. |
The voice recording's constant low-level hum was visible in the spectral view as dozens of narrow but strong bands of constant energy extending horizontally the length of the track. Like most of the unwanted sounds, these were completely invisible in the waveform view. To eliminate this, he found a place at the beginning of the file before the narrator began speaking where there was nothing but noise. He selected that, captured it as a Noise Reduction profile, and then applied it to the entire file. When the hum was removed, it was apparent that even in areas where the narrator was not speaking, some desirable ambient content previously obscured by the hum was retained.
To completely finish the file, Radeke said he might make several more passes with the Noise Reduction and then apply other traditional tools such as dynamic processing, a band limiter, and normalization.
After we finished the online conference and said our goodbyes, I reloaded my original noisy acoustic guitar file to try the Repair Transient command. Previously, I had zoomed way into the file and carefully carved out only the noises with the Marquee tool. But I was curious about the "healing brush" comparison and the Repair Transient's ability to preserve ambience by blending adjacent material around the deletion. For most of the squeaky guitar noises, there wasn't much difference in the sound between my surgical deletions and the Repair Transients process, because the squeaks were largely freestanding isolated events of differing frequencies.
But there was one place where it made a big difference -- a clicking sound right in the middle of a chord. I had painstakingly isolated and deleted the exact frequencies of the click within this chord, leaving small holes behind. It didn't sound bad the way I had done it before, but the Repair Transient command smoothed things out, leaving a fuller chord sound, while just as effectively removing the click. The next time I'm faced with a situation like that, the Repair Transient command will be the first place I turn.
And using the Amplify command to set negative values is also a great tip for situations where ambience needs to be preserved. It never occurred to me to use this for lowering the volume, only for amplifying it. Doh! But one thing I can vouch for is the power of the Noise Reduction filter for removing unwanted background noises like broadband hum -- I've used this quite effectively on several occasions to remove air conditioner noise, for instance.
As Radeke demonstrated, there is a wide range of applications for many of Audition's general editing tools in the spectral mode. Between Audition's traditional Edit view and the Frequency Space Editing workspace, users have dramatically different options for cleaning up a file. The Edit view is for processing time-based events, while Frequency Space Editing thrusts you into the third dimension of frequencies, as Radeke said. And having the same editing tools and effects available in either mode greatly expands their utlility -- and your ability to get things done.
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