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Digital Audio Principles

Sound tools pt. 3: Noise reducers, dither


From:

Digital Audio Principles

with Dave Schroeder

Video: Sound tools pt. 3: Noise reducers, dither

In this section, we're going to talk about two more sound tools that can be really helpful, in terms of dealing with noise and artifacts in your sounds. We'll look a little bit at noise reducers, and I'll show you a little example of that, and then we'll talk about dither. So noise reduction soundware, or sound tools, can help you eliminate things like pops and clicks that you might have on old vinyl records if you record them in, or different little static noises. You can use them to reduce things like background hum or other sounds. I'm going to actually go ahead and use one on a voiceover track that I recorded.
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  1. 50s
    1. Welcome
      50s
  2. 39m 10s
    1. What is sound?
      4m 15s
    2. Hertz and frequency response
      5m 34s
    3. Phase
      2m 39s
    4. Capturing audio
      3m 39s
    5. Sample rate
      6m 16s
    6. Bit depth
      9m 47s
    7. The waveform
      5m 3s
    8. Audio file formats
      1m 57s
  3. 7m 25s
    1. What is a digital audio workstation?
      2m 59s
    2. Typical DAW signal flow
      4m 26s
  4. 50m 33s
    1. What microphones do
      1m 57s
    2. Element types
      5m 0s
    3. Pickup patterns
      6m 51s
    4. Axis
      2m 52s
    5. Frequency response and the proximity effect
      5m 10s
    6. Phase issues
      1m 41s
    7. Microphone types
      8m 44s
    8. Miking vocals
      5m 39s
    9. Miking amplifiers
      2m 17s
    10. Miking drums
      10m 22s
  5. 16m 39s
    1. Cables and connectors overview
      2m 42s
    2. Balanced and unbalanced cables
      3m 19s
    3. Common cable types
      7m 13s
    4. Cable tips
      3m 25s
  6. 12m 16s
    1. What is an I/O device?
      1m 41s
    2. Analog to digital conversion
      3m 10s
    3. Tour of an audio interface
      4m 49s
    4. Interface considerations
      2m 36s
  7. 21m 5s
    1. What is a preamp?
      3m 21s
    2. Input levels
      5m 29s
    3. Padding
      2m 18s
    4. Phantom power
      2m 37s
    5. Phase reverse
      3m 4s
    6. Preamp demo
      4m 16s
  8. 12m 56s
    1. What is a mixer?
      5m 55s
    2. Input section
      1m 17s
    3. Channel strips
      3m 16s
    4. Master section
      2m 28s
  9. 18m 21s
    1. What is monitoring?
      2m 11s
    2. Speakers
      4m 47s
    3. Room considerations
      5m 43s
    4. Headphone types
      3m 50s
    5. Monitoring levels
      1m 50s
  10. 15m 23s
    1. What role do computers play?
      1m 36s
    2. Performance issues
      4m 11s
    3. Hard drives
      4m 38s
    4. Mechanical noise
      2m 10s
    5. Authorization
      2m 48s
  11. 6m 54s
    1. Planning for recording
      54s
    2. Doing a system check
      1m 26s
    3. Planning your inputs
      1m 42s
    4. The recording environment
      2m 52s
  12. 25m 52s
    1. Types of digital audio software
      38s
    2. Multi-track recorders/sequencers
      4m 56s
    3. Two-track recorders/waveform editors
      4m 55s
    4. Loop-based music production software
      5m 44s
    5. Plug-ins
      6m 56s
    6. Other varieties
      2m 43s
  13. 18m 59s
    1. Common components
      46s
    2. The transport
      2m 4s
    3. The toolbar
      3m 19s
    4. The Edit/Arrange window
      4m 42s
    5. The mixer
      5m 8s
    6. The file list
      3m 0s
  14. 19m 17s
    1. Setting up a session
      3m 30s
    2. Assigning inputs and getting signals
      3m 19s
    3. Input modes
      3m 28s
    4. Overdubbing and punching
      5m 14s
    5. Bouncing down
      3m 46s
  15. 19m 42s
    1. What is editing?
      1m 21s
    2. Waveforms
      2m 53s
    3. Making silent cuts and trims
      7m 1s
    4. Fades and automation
      8m 27s
  16. 1h 23m
    1. What are plug-ins?
      3m 0s
    2. Using plug-ins
      6m 11s
    3. EQs
      7m 4s
    4. Dynamics pt. 1: Compressors, limiters, expanders, and gates
      5m 40s
    5. Dynamics pt 2: Applying dynamic effects
      7m 2s
    6. Pitch shifting
      6m 14s
    7. Reverb
      9m 28s
    8. Echo and delay
      6m 23s
    9. Modulation effects: Phaser, flanger, and chorus
      9m 39s
    10. Sound tools pt. 1: About, gain, normalize
      7m 39s
    11. Sound tools pt. 2: Reverse and time compression/expansion
      6m 29s
    12. Sound tools pt. 3: Noise reducers, dither
      8m 11s
  17. 23m 43s
    1. What is MIDI?
      3m 6s
    2. Keyboard controllers
      1m 23s
    3. Computer-based virtual instruments
      1m 6s
    4. Control surfaces
      1m 6s
    5. Recording and editing MIDI
      12m 4s
    6. Virtual instruments
      4m 58s
  18. 27m 29s
    1. What is mixing?
      1m 54s
    2. Some common objectives
      3m 4s
    3. Some useful techniques
      5m 59s
    4. A quick mixing demo
      16m 32s
  19. 18m 48s
    1. What is mastering?
      2m 24s
    2. Sonic maximization
      9m 43s
    3. Final preparations and exporting
      6m 41s
  20. 13m 34s
    1. What is audio compression?
      2m 16s
    2. Popular formats
      2m 9s
    3. Bit rate, sample rate, and channels
      5m 42s
    4. Other adjustments and considerations
      3m 27s
  21. 15m 6s
    1. Essential gear
      7m 36s
    2. Voice recording setups
      1m 43s
    3. The voice production process
      5m 47s
  22. 10m 4s
    1. Analog vs. digital
      2m 48s
    2. Tube vs. solid state
      5m 6s
    3. The continual upgrade
      2m 10s
  23. 18s
    1. Goodbye
      18s

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Digital Audio Principles
7h 57m Appropriate for all Mar 02, 2007

Viewers: in countries Watching now:

Whether one is producing music, podcasts, game sounds, or film sound effects, Digital Audio Principles provides the tips and techniques that will make the project a success. Author Dave Schroeder explains the basics of digital audio production techniques and covers the essential hardware and software. He also discusses sound theory, frequency response, the range of human hearing, and dynamic range.

Subjects:
Audio + Music Audio Foundations Acoustics Microphones
Author:
Dave Schroeder

Sound tools pt. 3: Noise reducers, dither

In this section, we're going to talk about two more sound tools that can be really helpful, in terms of dealing with noise and artifacts in your sounds. We'll look a little bit at noise reducers, and I'll show you a little example of that, and then we'll talk about dither. So noise reduction soundware, or sound tools, can help you eliminate things like pops and clicks that you might have on old vinyl records if you record them in, or different little static noises. You can use them to reduce things like background hum or other sounds. I'm going to actually go ahead and use one on a voiceover track that I recorded.

We did a little interview in a kitchen, and needless to say, a kitchen is not the quietest place in the world to do an interview. There's quite a bit of noise and just kind of general machinery running around. I'm going to show you how we can apply a plug-in and actually reduce some of the noise a little bit. So let me get us a nice view of this, so that we can kind of listen to more of the voice and less of the noise. Let's just take a listen. (inaudible speech) So you hear that kind of that airy sound that there's a lot of noise there.

There may have even been, believe it or not, something like a refrigerator or air conditioner running in there. Lots of noise. So anyway, I want to try and get rid of that. I want to keep that voice. I want to keep hearing it. But I want to get rid of some of that noise as much as possible. So I'm going to go into the AudioSuite, then open up, from the Noise Reduction world, the X-Noise Mono plug-in, which is a waves plug-in. Again this is in Pro Tools, but you'll actually find stand-alone noise reduction software that if you have a sound file and you just want to bring it in and try and reduce the noise, you can do it as a stand-alone thing. Or you can find lots of plug-ins that will work with your digital audio software.

So the first thing I'm going to do is teach my noise-reduction software to go ahead and learn what this noise sounds like, to kind of memorize what the noise is. So I'm going to highlight something that's just noise, and I'm going to go ahead --and here, we call it learning that. Let that run through a few times. Okay. So now we've got what it thinks is the noise.

So now I'm going to go ahead and highlight a little bit more of this section and preview it through our plug-in. And then I'm going to bring up the threshold for this. (inaudible speech) So can you hear the difference there? We've reduced the amount of noise pretty well. It's not completely gone, but we can hear more of the voice. We'll A/B it and compare it.

I'll play it, and then I'll bypass it, so we can hear how much noise was originally there. (inaudible speech) So that's a lot more palatable now. Of course, we can go farther, and I will; I'll show you. One thing I should mention that with a lot of noise-reduction software is ultimately the way it works is it's actually taking away some of the frequencies. It's turning down specific frequencies and certain volumes, and at some point when you start to do that, you also start to take away some of the frequencies, or sound information, or material that's the material you want to hear.

In this case, the interviewee's voice. (inaudible speech) So you can see that we can actually do quite a bit to reduce the difference between noises. Let's A/B it one more time, and see what a difference we have made. (inaudible speech) So you can hear that the quality of the voice does change a little bit and fine- tuning your noise-reduction software, it takes a lot of time and a lot of love.

You've got to get pretty close to it and spend some time with it, because there's always just the perfect balance between getting rid of as much noise as you can and starting to affect the sonic quality of what you want to hear, or her voice. So it takes a little bit of playing, but in certain circumstances it works like a charm. It kind of all depends on what the noise is like. If it's a constant and kind of consistent flowing noise like that, it's a lot easier to zero in on it, kind of learn it and give it a profile, and then reduce it a little bit. If it's kind of erratic and coming and going, you won't have as much luck reducing the noise.

But I think a little bit less noise is still better than all that noise. So it's something to look into it. Now let's take a look at dither, or dithering. Now this could be one of the least interesting plug-ins to look at, and I should explain what dither is. When we work in a session like this, I'm in a session with a bit resolution of 24 bits or 24 bit depth, when I want to change that bit resolution to any lower resolution, like 20-bit or 16-bit, we effectively have to re-sample the sounds. And the reason you want to go to a different bit depth is that if I want to put this on an audio CD or even use it as a source file to generate an MP3 from, I need to dither it down to 16 bits.

So we're working at 24 bits, and I want to go to a 16 to put this on a disc. In other situations, you might find yourself working at 32 bits and needing to downsample down to 16 bits. Well, what happens is we have to re- sample that sound, and with digital re-sampling and downsampling, a lot of times you run into trouble with some of the quieter passages in your sound file. The sampling can have a tendency--it doesn't always happen--but it can have a tendency to introduce a little bit of distortion there, because basically it's not seeing enough. It can't quite find enough information to sample, and so it gets a little confused.

It wants to find something, but it doesn't quite find it. So what dithering is, it's the act of actually adding in very, very quiet noise, so that there's some program material there. There's some data that the sampler can look at and pay attention to, and it reduces the possibility of there being little artifacts, or little moments of slight distortion. Now in a lot of scenarios, dithering is not absolutely necessary, and you might not even notice that you didn't dither. The effect might not be noticeable. But sometimes it will happen, and you'll hear little artifacts in your new 16-bit sample, and you'll wonder where they came from.

Well, dither is what you want to apply to the file before you export it. So let's assume we have a master nix. It's pretty simple. You open up the tool and you decide what bit rate you're headed for. So were headed to 16 bits, see? Here I have the options of 20 bit and 16 bit. That's because I'm at 24 bit. I have to be going down in some direction, so we're going to go down to 16 bit. And all you do is select your sound file. If it's your final mix that you bounced everything to, select it, hit Process.

It won't look that different. It won't sound that different to you, but something good is taking place. So we'll go ahead and just apply it, so we can see it. Really not even that big of a difference when you go to play it back here in this situation, slightly, but nothing to go crazy about. But the point is, if you have it and have access to it, it's wise to do it in order to avoid the possibility of getting some distortion and some artifacts.

We'll talk a little bit more about this in the chapter on mastering. So that does it for sound tools and for plug-ins in general. Hopefully, I've shown you enough of what's possible and kind of what different plug-in families do and the different kinds of effects they have, so that you can go and start to play with different plug-ins and look into the different kinds of digital signal processing that you want to use for the work you're doing.

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