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We've seen how Audition can be a big help when you have an audio file with unwanted noises. Using the Spectral Display, you can quickly identify and remove or heal pops, licks, and other problematic noises. Now, as I also mentioned previously, these tools are great for relatively short sounds. But we also come across audio files that have much longer unwanted sounds that appear throughout the entire track. This could be a noise like a tape hiss or power line hum or just the natural ambient background sound of where the recording was made. For those types of situations, you can use Audition's Noise Reduction Effect. It works by examining a sample of the background noise that you select, and then it tries to remove that sound throughout the entire file.
I'm going to go ahead and open a file. Let's go with the interview_BD file again. And let's just split this so we can see both the Waveform Editor and the Spectral Display, and I'll play a little bit of it. (male speaker: Well, we have one farm in Ojai, where we've been since 1998, and that is, really, an urban farm. We are in the city limits--the last property in city limits--and we're about one minute from a giant shopping center--) So this was recorded outdoors, and there's a lot of ambient noise.
Now that may be something you want to keep and not completely eliminate. It depends on what you're trying to do with your file. But first, let's capture the noise print. The idea here is to select a portion of the recording that contains just the background noise and no sounds that you want to keep. You can see very clearly here in the Waveform Editor where the dialog is and is not. And in the Spectral Display--let me make this a little bigger--you can also see where our speaker is talking. It's all the bright spots along the bottom of the Spectral Display, and you can also easily see the background noise, the purplish speckles throughout that sort of fill out the entire display.
So in order to capture a noise print, basically a sample of the noise we want to remove, we need to select it. I'm just going to switch back to the Waveform Editor for this. At the very beginning of this file, we have about a second and a half before our subject starts speaking. So I'm going to bring in my selector here and to select just that silence. Ideally, you want a selection that's at least half a second in length. You might want to loop your selection a few times, and I do have the loop turned on here, to make sure you're only selecting background noise. (audio playing) So I have no speaking in there right now.
Once you have made your selection, go to the Effects menu, to Noise Reduction/Restoration, and you're going to want select the Capture Noise Print. Notice the keyboard command for this is Shift+P. That's a good one to remember if you do this a lot. I get this message telling me that my current selection is going to be captured and loaded as a noise print, and it's this noise print that Audition will use when I run the Noise Reduction Effect. I'll click OK. So let's do that, let's run the Noise Reduction Effect. I'll go back to Effects > Noise Reduction/ Restoration and choose Noise Reduction. Notice its keyboard command is Shift+ Command+P, on Windows Shift+Ctrl+P. Since the Capture Noise Print and the Noise Reduction Effect are used in conjunction so often, their keyboard commands are very similar.
Okay, so this is the Noise Reduction window. Now, unlike when you have a windows floating above your main window in other applications, you can still control Audition even though the Noise Reduction window is floating on top. For example, if I wanted to get a different selection from my Noise Print, I can move this window over, make a selection and then click Capture Noise Print. I can even still use the Playback controls down here at the bottom. (audio playing) But I'm going to use the Noise Print that I originally captured and you can see here that it says Noise Print Currently Set Noise Print, which is the most recent Noise Print I took.
So I'm going to click to deselect that so I'm not listening to just that section. Now, you can see the Effect is currently powered on, so I'm going to click Play. So let me roll this back to the beginning. You can see the playhead is back at the beginning now. So I'll click Play. (male speaker: Well, we have one farm in Ojai, where we've been since 1998--) And you should already be able to tell that the level of background noise has been reduced. While it's playing, you can toggle the effect on and off with this Power button here so you can compare the before and after.
(male speaker: --and that is, really, an urban farm. We are in the city limits-- the last property in city limits-- and we're about one minute from a giant shopping center, and you would never even know that it was here.) So we can definitely tell that the noise reduction is working. It does sound a little bit boxy right now, but only a little bit, and that's some of the trade-off you get when you're removing background noises. Not that you have to be content with the default settings here. You probably want to play around with the Noise Reduction and Reduce by sliders.
Noise Reduction determines how much of the Noise Reduction Effect you want to apply, and Reduce by determines by how many decibels you want to reduce the noise. Notice that I moved the Noise Reduction slider to the left, the green areas in the graph up here move as well. What we're seeing here is a Noise Floor Graph. It depicts the frequency of a noise along the horizontal or X axis and the amount of noise reduction along the vertical or Y axis. Looking here on the graph I can see that the lower frequencies, the ones on the left are louder than the higher frequencies in the Noise Print Recaptured. The yellow dot shows the highest volume of noise in each frequency.
The red dot shows the lowest volume in each frequency. And green shows the volume you're setting the Noise Reduction to. So at 100% Noise Reduction, all the noise we sampled is being eliminated, which is why the yellow dots are hidden behind the green. And if I drag this down all the way, that's the equivalent of No Noise Reduction at all. Again, you have to listen to your own recordings to determine how much noise you want to remove with the Noise Reduction slider and then how much you want to reduce it by with the Reduce by slider. So it's a good idea to just loop your audio, have the Loop button on here, let it play, and then play with the sliders to suit your ears.
(male speaker: Once you're out on the farm, you just feel like you're in some rural area, so that's the best of both worlds for me, because I have children, they're in school in town here, there's a big community of students, parents, friends that are close by, so we get to do our farming--) So that sounds pretty good to me. Now, using this Noise Reduction slider is just a one way to adjust your Noise Filter. It can be a little bit heavy handed since it reduces the effect on all frequencies evenly.
There may be cases when you want to target specific frequency ranges to reducing volume. To do so, you can click the handles in this blue line that runs across the graph and you can drag them up or down. And you can click anywhere else on the line to make additional handles to apply Noise Reduction to particular frequencies. Again, it's something you'll have to play around with on your own, and you may find different levels of success with it, depending on the files you're working on. If you mess things up too badly, you can click the Reset button here. For this one I'm just going to leave it as a flat line, and I'll make sure that I'm applying this effect to my entire file by clicking Select Entire file, and then I'll click Apply.
Audition takes a few seconds to process the effect, and there it is. You can really see the areas of sounds now are more flatlined instead of the little fuzzy lines that we saw between the speaking before. Now if I look at the Spectral Display, you can see a lot of the purplish specks have been eliminated from the background here as well, indicating that a lot of the background noise has now been removed. And if I play my file, I should be able to hear that difference. (male speaker: --in very close proximity to the rest of our life, and that our other--) So that's how to reduce or remove background noise from your audio files.
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