What you can and can’t fix

- [Voiceover] Noise reduction can be a huge help to any project sound design. But what kinds of noises can be reduced and how far can we go? I'd like to shape our expectations for what can and can't be done by noise reduction and restoration. Most noise problems can be mitigated drastically by following my advice from the Production Techniques chapter of this course. Make sure your signal-to-noise ratio is good. That way the noise you need to reduce will be far lower than the signal you wanna keep. And you'll be less likely to damage or harm the good audio as you remove the bad audio when you're noise reducing. And that really describes the trade off we're always wrestling with when we're doing any noise reduction. We're trying to preserve the good audio with as little coloration or sonic artifacting as much as we can when we lower the bad stuff. That sounds easy but it's much harder than it sounds. Let's talk about the three main types of noise problems. First, we have tonal noise and hum. These are constant tonal noises that exist in the frequency spectrum of any sound. The sources are from machines like refrigerators or any kind of motor. Air conditioners are also culprits. Here's an example. - [Voiceover] Fasten your seat belts and prepare yourself atmospheric reentrance. - [Voiceover] The dialogue sounded great but we had that hum behind the dialogue. Tonal hums or tonal noise problems can also be something moving around the frequency spectrum, like a siren. So, it's a constant noise but it's moving up and down the frequency range right when someone's talking. Here's an example of that. - [Voiceover] All right, well after spending some time at what can only be considered the epicenter of Times Square, we walked a little bit further. We were still in the middle of the action but when we saw the huge American flag lit up with LED lights. I mean, it's such a powerful icon that I thought-- - [Voiceover] So, that example actually has two types of noise. It has a tonal noise, which is the siren, but it also has broadband noise. And that's the next category. Broadband noise is the toughest of the bunch. It comes in the form of air conditioning, traffic noise, and other noises that scatter all of this frequency spectrum. So, in the last example we heard the siren, that's the tonal part. We heard just a basic traffic wash behind the subject that's speaking. Here's another example of that. - [Voiceover] A place where there's something there. And then I can sort of stay put and let people walk through and they create the photograph. - [Voiceover] So, we hear his voice but behind his voice we have a wash of city sound. Now, in that case it wasn't so bad. But again, if we try to turn this sound clip up, all that noise is going to come up as well. So, we might want to use some sort of noise reduction to help get rid of the broadband noise as well. The next category of noise is something we call intermittent noise problems. These are digital clicks, digital pops that might make their way into a recording because of say a bad cable or a bad digital connection. These could also be lavalier mic hits. So, could be radio hits or even the actor physically hitting the lavalier mic or their clothes rubbing against it. That would be considered intermittent noise problems. This also could be something like boom pole bumps. So, the boom operator hit the pole on something and we get a boom, a big bump, an intermittent noise problem. One other thing that falls in this category are things like birds. So, birds chirping throughout a clip would be considered intermittent noise problems. And these can be taken care of on a case by case basis. And we can use some noise reduction techniques, even just simple editing, to take care of some of these noise problems. - [Voiceover] Ladies and Gentlemen, we are approaching Mars lower orbit. Fasten your seat belts and prepare yourself for atmospheric reentrance. - [Voiceover] So, that example, again, had really clean voice but behind it was a whole bunch of crackling. So, that would be a perfect example of some of the intermittent noise problems this time coming in the form of clicks and pops. Now, that we know how to identity possible noise problems, we'll take a look at how we can address and deal with these noise problems in Adobe Audition in the next few videos.