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Applying compression

From: Audition CS6 Essential Training

Video: Applying compression

So now I'll start taking a look at some of the specific effects that come built into Audition. Probably what makes Audition so attractive as an audio editing application is the sheer number of effects that it comes with. Let's begin by talking about Compression. I'm working with the file singrealloud.wav. Let's go ahead and play this once. (music playing) So as you can hear and also see by looking at the waveform, there is a significant dynamic range between the four phrases of the performance captured in this recording.

Applying compression

So now I'll start taking a look at some of the specific effects that come built into Audition. Probably what makes Audition so attractive as an audio editing application is the sheer number of effects that it comes with. Let's begin by talking about Compression. I'm working with the file singrealloud.wav. Let's go ahead and play this once. (music playing) So as you can hear and also see by looking at the waveform, there is a significant dynamic range between the four phrases of the performance captured in this recording.

This is due to the way the singer performed the song, and there's no fault in that. You don't want to ask a singer to be less expressive, you want to capture a good performance. The problem is that the quieter parts of the recording may get lost in the mix once you start adding in other instruments. Or even if this was meant to be an A capella performance with no other accompaniment or instruments, you'd still want to do something to slightly decrease the dynamic range within the recording so the listener doesn't have to turn up the overall volume just to hear the quieter parts or turn down the volume so the louder parts aren't overbearing. Compression helps you get a consistent volume level throughout your file.

Compression attenuates or reduces the loudness of the loudest portions of your recording, so there's not as much of a difference between them and the quietest portions. This allows you then to increase the overall volume or gain, so the entire file can be as loud or even louder than the loudest parts originally were. Now I don't have the ability to give you a really detailed explanation of all the aspects of compression techniques here, but I do want to show you some basic techniques so you can see what Audition is capable of. If you'd like to learn a lot more about Compression, be sure to check out the course called Foundations of Audio Compression and Dynamic Processing on the lynda.com Online Training library.

Right, so let's take a look at some Compression effects. Now as we saw previously you can apply effects either from the Effects menu or the Effects rack. And we recall that the Effects rack gives you much freedom and flexibility to make changes so you should use it instead of the Effects menu. But for the purposes of this demonstration, I'm going to use the Effects menu because you'll be able to instantly see the changes I make reflected in the appearance of a waveform, whereas with the Effects rack, I'd have to click Apply each time I make a change. But when you are applying effects for your own work, you'll want to use the Effects rack. So I'm going to go to the Effects menu and choose Amplitude and Compression.

And here I want to look at the Single-Band Compressor start. Now pretty much all of these effects here are Compressor effects as well, but I want to focus on the Single-Band Compressor. A Single-Band Compressor means that it's going to affect all of the frequencies equally throughout your recording. You will see in a little bit that a multi-band compressor lets you apply different compression to different frequencies but a Single-Band Compressor affects all the frequencies equally. And we have five sliders here. The first one is Threshold and it's determined by decibels. Threshold has a decibel level at which the compressor reacts or is triggered.

When the amplitude of your audio rises above the Threshold, the compressor applies the compression settings basically what you have set up here under the Threshold slider. When the amplitude of your audio is below the threshold, the compressor does nothing. So looking at the waveform of my recording here, I can see that the loudest points reach a little bit over -9 dB. I can see -9 dB on the scale here, and if I follow that line over. This would probably be the loudest point right here. So a Threshold setting any higher than that would have no effect on any part my recording. A Threshold setting of say -15 dB or so would affect the louder portions but have no effect on the two softer phrases since neither of them really go over -15 dB.

So the Threshold determines when the compressor actually compresses. But how much it compresses is determined by the ratio setting, which is the next slider here. The ratio determines how much any signal over the Threshold is attenuated or reduced, and it's usually expressed as a larger number over one or a ratio. Right now, the ratio is set to 1:1. The higher the ratio, the more severe the compression. A ratio of 1:1 has basically no change, a ratio of 2:1 reduces the original signal by half, a 4:1 ratio reduces the signal to a quarter of its original amplitude, and so on.

Generally a setting of 2:1 to about 4:1 is common. Anything higher than that is considered extreme compression but where you set your ratio is really going to depend on your recording and what you're trying to achieve. So if I want to even out the dynamics of this recording, I want to look at the peaks of the quieter portions of the recording. And the quietest portion is definitely this phrase here on the end. And looking at the scale here it looks like they go to about -24 dB or so. So I'm going to set the Threshold to -24 dB. And now we know that anything louder than that will be affected by the compressor.

That basically means the rest of the recording will be affected by the Compressor while this quietest phrase will not. For the ratio, I'm going to go a little bit more extreme since there's such a wild degree of difference between the loud and quiet parts of this recording. Let's try about 8:1. Now the Attack setting determines how quickly the compressor reacts when it detects a signal that goes above your Threshold. The release slider is for specifying how quickly the compressor lets go of that signal and returns it to its uncompressed state after it detects that the audio is no longer above the Threshold. Notice that these two are measured in milliseconds so the attack and release happened very quickly in most cases.

But they can have a noticeable effect on the sound of your recording. Too long an attack time and the compressor may not attenuate the louder signals quickly enough. Too long a release time and the compressor effect might be applied to quieter sounds that don't need compression. Again, it's something you'll have to experiment with. I'm just going to leave them where they are for now. I'm also going to leave the Gain level at zero right now. Let's click Apply and see what the results of these settings look like. So now you can see the waveforms are much closer to each other in height. Let's give this a listen. (video playing) So we have a much more even dynamic range now in this recording.

But as you can see, one of the obvious effects of compression is it reduces the amplitude of you recordings. That's why you have like a Gain slider to adjust the output level of your recording after compression has been applied to bring the level back up closer to where the loudest points were before compression. So first, let's note that the loudest portions of this recording are now at about let's say -18 dB. So before compression the loudest parts were around -9 dB or so. So we had about a 9 dB reduction in amplitude. I'm going to undo the Single-Band Compressor effect, and I'm going to open up the Effect again.

So my previous settings are still in here, but this time I'm going to increase the up again by about 9 dB, and that's going to bring the level back up to where the loudest portions of my recording where before compression was applied. I'll click Apply. So now I have applied the compression but also increased the amplitude of the entire file. Now with the settings I've applied and at the scale you can still see a difference between the louder and quieter phrases in this recording but the difference between them isn't nearly as severe. And generally, you don't want to apply so much compression that everything in a vocal performance is exactly the same level, doing so robs your recording of all dynamic range.

And let's just play this once. (video playing) Now you also shouldn't get too caught up in the numbers. Applying compression has a lot to do with just using your ears and looking at the waveform and settings as a guide. It's really about training your ears. For most basic compression tasks, you can generally start by lowering the Threshold to a level that is about 4 to 6 dBs of Gain reduction. Then use the Gain slider to raise the output to about the same level as the highest peaks before compression.

But again, that's just the starting point and you can experiment from there. Let me undo that again and open the compressor one more time. You might have noticed that this compressor like many of the other effects has some presets you can choose from. One good way to learn how compression affects your audio is to select your preset and see how it changes the sliders, then click Apply and check out your waveform. If it's too much or too little after you listen to it, you can always undo it and then pick another preset.

And remember, you can always play your audio while you're working on the settings. (video playing) I'm just going to close out of that for now. And of course, it's also much easier to experiment if you're using the Effects rack. Remember you can come in here and choose your effect and try different settings, and if you don't like the settings you can always just come back in here and change them again.

I'm just going to right-click on this and remove the effect. So that's the basics of Compression. Now as you start to get more comfortable with Compression, you can start working with the multi-band compressor. It's divided into different bands of frequencies and you get an individual compressor for each frequency band, from low to mid to high and then anything above high which by default is anything above the 10k range. The available settings under each band or the same we were just looking at in a Single-Band Compressor, we have threshold, gain, ratio, attack, and release, but here they apply to the specific frequencies.

I'm not going to get into all the details of the Multi-band Compressor here, but if you understand the basics of what we've just gone over, you'll get the idea. But again, Compression is a huge topic and an important one to understand. So be sure to check out the title I mentioned earlier called Foundations of Audio Compression and Dynamic Processing to get the full story.

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This video is part of

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Audition CS6 Essential Training

56 video lessons · 22980 viewers

Garrick Chow
Author

 
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  1. 1m 7s
    1. What is Audition?
      1m 7s
  2. 1m 55s
    1. Welcome
      54s
    2. Using the exercise files
      1m 1s
  3. 21m 6s
    1. Understanding the Audition interface
      8m 49s
    2. Setting up input and output
      4m 7s
    3. Setting essential preferences
      8m 10s
  4. 25m 3s
    1. Importing audio files
      6m 39s
    2. Extracting audio from a CD
      4m 6s
    3. Importing video files
      2m 21s
    4. Recording audio
      4m 50s
    5. Creating a multitrack session
      7m 7s
  5. 8m 8s
    1. Understanding frequency
      1m 50s
    2. Understanding amplitude
      1m 40s
    3. Understanding sample rate
      2m 34s
    4. Understanding bit depth
      2m 4s
  6. 37m 59s
    1. Understanding the Waveform Editor interface
      6m 2s
    2. Making selections
      6m 5s
    3. Adjusting the clip amplitude
      2m 49s
    4. Fading clips
      4m 5s
    5. Normalizing
      5m 17s
    6. Copying, cutting, and pasting
      7m 40s
    7. Undoing, redoing, and using the History panel
      4m 5s
    8. Generating silence
      1m 56s
  7. 24m 1s
    1. Using the Spectral Frequency Display
      2m 53s
    2. Using the selection tools
      7m 18s
    3. Using the Spot Healing Brush
      6m 34s
    4. Removing background noises
      7m 16s
  8. 46m 31s
    1. Understanding destructive vs. nondestructive effects
      12m 35s
    2. Applying compression
      9m 20s
    3. Understanding reverb vs. delay
      4m 44s
    4. Working with filters and EQ effects
      6m 46s
    5. Using special effects
      4m 26s
    6. Isolating vocals in a stereo track
      4m 27s
    7. Working with time and pitch effects
      4m 13s
  9. 1h 18m
    1. Creating a multitrack session
      6m 1s
    2. Recording and importing audio
      9m 42s
    3. Understanding the multitrack interface
      5m 20s
    4. Understanding the Mixer panel
      6m 13s
    5. Editing clips in Multitrack View
      9m 49s
    6. Grouping clips together
      2m 43s
    7. Creating bus groups
      7m 42s
    8. Routing and working with sends
      4m 7s
    9. Using automation
      12m 25s
    10. Pre-rendering tracks
      2m 19s
    11. Exporting the mix
      4m 13s
    12. Exporting the session
      3m 22s
    13. Burning the mix to a CD
      4m 45s
  10. 25m 17s
    1. Working with audio from video
      6m 23s
    2. Importing a sequence from Premiere Pro
      3m 59s
    3. Adding a soundtrack to a video
      3m 45s
    4. Exporting a session back to Premiere Pro
      3m 32s
    5. Using Automatic Speech Alignment
      7m 38s
  11. 9m 46s
    1. Understanding the interface
      6m 17s
    2. Using pan envelopes
      2m 44s
    3. Exporting a multichannel mix
      45s
  12. 52s
    1. Next steps
      52s

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