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Sony Vegas Tips & Tricks: Audio Normalization and Noise Reduction
Posted Jan 31, 2009 - February 2009 Issue Print Version     Page 1of 1
  

Welcome to our latest tutorial on Sony Vegas! This month’s topic is audio. But before we get into dealing with audio in postproduction, allow me to get on my soapbox about videographers obtaining quality audio in the first place. Strive to get the best-quality audio you can right up front! It’s been said that audio makes up at least half of what you “see” in your video. What does that mean? It means that the audio component of our work is actually judged more critically than the video component. Your audience may not even notice—or will at least forgive—shaky video or poor color, but even the slightest audio dropout is noticeable. Be sure to spend enough time planning how you will acquire the audio for your productions. This may include any combination of the following: lapel mics (wired or wireless); field recorders such as those from Marantz, Edirol, or the wedding darling iRiver; boom mics with operators; hand-held mics; and camera-mounted mics. I know shooting live events can be tricky, but most of us can do a better job at it. But for those instances when your captured audio leaves something to be desired, it’s great to have postproduction tools that can make a difference. Sony Vegas actually started life as a multitrack digital audio workstation (DAW) prior to being a video powerhouse, and it still boasts the best complement of audio features of any NLE on the market.


Step 1: Drag an Audio File Into the Timeline
Let’s take a look at what Vegas dials up automatically with every audio track. Drag an audio file to the timeline. Click the Track FX button on the Track Header, and you’ll see that by default you already have an EQ, Compressor, and Noise Gate on every audio track (Figure 1, below).

Sony Vegas Audio Plug-in

These are some of the most common tools used in audio work. Although these tools are already assigned to your track they are always set by default to neutral, or a “no-effect” state. We’re going to skip over these basic tools for now, but we will talk about the Compressor in a later article.

Step 2: Check Your Levels
Before jumping into the tools, let’s check our levels. View the basic audio mixer in Vegas by choosing View – Mixer (Figure 2, below).

Sony Vegas

Step 3: Open the Levels Editor
Play your audio track in the timeline by clicking the spacebar, pressing the L key, or clicking the Play icon. Where do the levels hit on the mixer? A general rule of thumb is that your audio should peak at -6dB. You can go as high as 0, but should you? Probably not, but it depends on your application and your audience. A lot of current pop and rock music is mixed in such a way that everything is normalized, compressed, and squashed to hit consistently at 0dB. There is no dynamic range, there are no perceived peaks and valleys in the volume, and it fatigues listeners.

Then again, have you ever noticed how the commercials on TV are “louder” than the program? It’s because they’ve got only a few seconds to grab your attention, and the same concept of keeping the audio constant at 0dB is employed. In any case, you must never go higher than 0dB because you’ll end up with digital distortion. Your mixer will show you when you go higher than 0 by displaying the dB level in red (Figure 3, below).

Sony Vegas

Step 4: Adjust Volume Over Time
You can adjust the volume of your audio track over time by using a Volume Envelope and setting envelope points. Click on your audio track to select it. From the menu, choose Insert – Audio Envelopes – Volume (Figure 4, below).

Sony Vegas

You can double-click anywhere on the envelope band to create a point. Next, left-click and drag to adjust the volume up or down as needed. Remember, your mixer is the monitoring device you’ll use here to check the overall sound levels. As you add audio tracks, your overall combined volume will increase. This is where mixing becomes an art. Since your overall output should ideally stay around -6dB, some tracks may need to increase in volume while you may have to reduce the volume of others to get the proper mix.

Vegas Pro allows you to have an unlimited number of audio and video tracks. When you’re dealing with many audio tracks or when you’re working on an audio-only multitrack project, it’s helpful to use the Mixing Console view, which emulates a recording studio’s mixing console. From the menu, choose View – Mixing Console. For the purposes of this article though, we're sticking with the standard Vegas mixer described earlier.

Step 5: Choose Switches to Normalize
The next procedure I want to discuss is normalization. In Vegas, normalization is found by right-clicking the audio event and choosing Switches – Normalize. This tool is used to adjust the overall level of the audio. Vegas takes the loudest peak of the event, sets it to 0dB (at the event level), and everything else in the event is set relative to that. This is called Peak Normalization. Sony Sound Forge, a more detailed and specific audio tool, can do RMS Normalizing, which raises the volume based on the average level of the audio event, instead of the peak. Since both products come from Sony Creative Software (Sound Forge is sold separately), there is a natural integration between the two. You can start with all of your audio events in Vegas and perform more detailed surgery on them with Sound Forge as needed, for an extreme amount of fine-tuning of your audio.

But for this article, we're going to do Normalization from Vegas only. To Normalize your audio track in Vegas, right-click the event and then choose Switches – Normalize (Figure 5, below).

Sony Vegas

Step 6: Look for Peaks in the Audio Waveform
The “Switch” paradigm is equivalent to “flipping a switch” on a mixer’s input channel. Once normalized, you may notice the waveform has changed its shape. Play the timeline. Do you hear any difference?

Depending on the original audio file, you might not. But if the volume was recorded low to begin with, it will now be louder. Any peaks in the file will be adjusted to 0dB. Let’s say, for example, our audio is of a mumbling groom. In our audio sample you can sort of hear the groom, but you can definitely hear where he fumbled with his tie and brushed the microphone, creating an unwanted peak (Figure 6, below). The same could be true of a cough, a sneeze, or some other transient sound.

Sony Vegas

Step 7: Isolate the Peak
When you normalize, you set the loudest point of the event to 0dB. (Remember, in Vegas we have Peak Normalization.) The loudest point was when the groom brushed the mic with his hand. As you can see, everything else in the event is much lower in volume. In this example there is no difference between before normalizing and after, because the brushing of the mic is the loudest thing in this event and is already peaking at 0db.

One thing you can do to fix that is to isolate that peak away from the other audio and normalize again (Figure 7, below). Set your cursor just before the peak and click S for split. Then set your cursor to just after the peak and click S again.

Sony Vegas

Step 8: Insert a Volume Envelope and Add Points
Ctrl-click each event on either side of the unwanted noisy peak, right-click, and again choose Switches – Normalize. (If Normalize is already checked, do this twice to uncheck it and then check it again.)

Your audio has now been chopped into three events: The first and third events have the audio content normalized such that everything is louder, and the second event is the original peak of the brushed mic (Figure 8, below).

Sony Vegas

You can further adjust the loudness by inserting a volume envelope as previously described and inserting your volume points where needed.

Step 9: Isolate the Noise

As you listen to your audio event, does it sound noisy? Maybe you recorded a person talking in a noisy room, and when the person pauses between sentences you can hear the background chatter. Or perhaps you were located next to a humming air conditioner vent when you were filming, or you were in some other industrial environment where a constant noise or hum was present. Or if the audio was recorded too low and then brought up via normalization, there may be some background hiss. A Noise Reduction (NR) plug-in can help eliminate hiss, hum, and other types of noise.

NR is not included with Vegas Pro, but it is one of the first audio plug-ins I recommend getting. As a stand-alone plug-in it’s available for purchase from Sony Creative Software, but it’s also included with the previously mentioned Sony Sound Forge audio editor (but not with the Sound Forge Audio Studio lite version). The NR plug-in alone makes buying Sound Forge a great value. If you have Sound Forge installed, you can use the included NR plug-in directly from within Vegas without having to open the audio in Sound Forge if you don't need to.

The idea behind NR is simple once you understand it. Let’s say your audio is of a person talking directly into the camera mic. When you recorded it you didn’t realize you were standing near an air conditioner vent that produced a constant hum. But once you got into the edit, the hum is all too noticeable (Figure 9, below, left). See how the “quiet” portions of the waveform aren’t quiet at all? This program material is all noise. Having at least a small section of “just noise” in your audio is crucial to using the NR plug-in. We’re going to “teach” the NR plug-in which part of our audio is noise so that it will learn the frequencies to operate on. First, place the selection cursor on the timeline at a point where the only audio is noise. Next, click the Track FX button to bring up all the plugins on this track and click the “Plug-In Chain...” button (Figure 9, below, right).

Sony Vegas

Step 10: Select the Noise Reduction Plug-in
Select the NR plug-in for your audio track by double-clicking on it from the list of effects that comes up. This assumes that you have either installed Sound Forge with the NR plug-in or installed just the NR plug-in by itself. Either way, once the plug-in is installed, you will see it in the list of effects available for Vegas Pro (Figure 10).

Sony Vegas Plug-in Chooser

Step 11: Capture a Noiseprint

In the NR plug-in in the chain, select the Noiseprint tab. Think of noiseprint as a thumbprint, something that uniquely identifies the noise. Check the box for Capture noiseprint (Figure 11, below).

Sony Vegas

Step 12: Identify the Noise and Reduce It
When you are ready to have the Noise Reduction “learn” what you’re identifying as noise, click the very top bar of the main Vegas window to get focus back to the main program. Click the L key to start playback from the current position of the cursor.

The NR plug-in instantly grabs hold and learns what to recognize as noise. Wait 1 second and click the K key to stop playback.

You may find that once applied the overall timbre of the audio has changed, perhaps to a point of sounding robotic and unnatural. The NR plug-in uses very specific equalizers and filters to work its magic; it isn't always perfect. You can adjust the amount of noise reduction that is applied to your file by adjusting the slider labeled Reduce noise by (dB) (Figure 12, below). The default amount of noise reduction applied is 12dB, but you may find you need more or less. If you find you need a lot more, you can even chain together instances of the NR plug-in one after the other.

Sony Vegas

Practice using noise reduction on several different audio files to get the feel of how the plug-in works. This is one of those tools that can really clean up your audio tracks. If you have just a little noise in the background, this plug-in can make it whisper-quiet; if you have so much noise that you think the track is unusable, try the NR plug-in on it. It might just save the day.

I hope you have found this article informative and that it helps to improve your audio work in Sony Vegas. Next time, I’ll talk about chaining audio effects, using the audio tools built into VASST Ultimate S Pro, and audio settings for DVDs.

David McKnight  (david at mcknightvideo.com) is half of McKnight Video of Houston. He is vice president of the Houston Professional Videographers Association, has Sony Vegas and HDV certification, is the technical editor of Vegas Pro 8 Editing Workshop (Focal Press), and is a contributor to TheFullHD Book (VASST). He and his wife, Christie, are winners of multiple HPVA awards.

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