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Fixing Pops & Clicks Using iZotope RX with Warren Sokol

Transcript
There are continuous noises and intermittent noises, like pops and clicks, and stuff like that.

A lot of times, you might tend to do them in a certain order. The reason for that being is that it can kind of be like peeling an onion, in that if I remove the broadband noise, it can show some other noise. And a good example of that is if someone has recorded to tape originally, and it’s been ten years now, and that tape’s been transferred a couple of times, you could remove what seems like this layer of noise, and you remove it, and that was the noise from the loudest tape machine, so now you’re left with a second generation of a different kind of noise, and that can confuse the algorithm and give you bad noise reduction artifacts.

So anyway, when you’re doing noise reduction for tape, it’s always best to try to get the earliest version, because of just that. The noise itself can build up and cause problems and peel away. Removing one tick can show there were actually pre-ticks or post-ticks that you weren’t hearing, because it was masking the other ticks.

So anyway, noise reduction is a weird thing, and more than likely, as we start doing some stuff, there’s going to be a lot of going back and forth and trying this, and trying that.

Real quick, just to kind of — I’d mentioned that there’s kind of a process and order to it. There’s no rules, but I’ve got some notes here just because I didn’t want to forget this, but in general, if you’re attacking a horribly — I shouldn’t say horrible — let’s say you have an old vinyl that you needed to transfer and clean up.

The general order is tonal artifacts. You’re going to get rid of buzzing and humming and that kind of thing first. Then you want to get rid of the ticks and pops — the loud ticks and pops that stick out. Depending on the system you’re going to be using, there can be an automated tick removal and manual tick removal.

Automated tick removal can get a little carried away with itself by removing transients like snare drum hits or cymbal crashes can get messed up, that kind of thing. The transients and ticks can get messed up with the automated, so if you are going to run an automated pass first, it’s best to run it at a very conservative level, then go back, listen through, and get rid of the other ticks that need to be removed manually.

As far as tick removal, there’s a number of different ways to do it. Most noise reduction suites will have a de-tick or de-clicker program. There’s also a new type of — I shouldn’t say new, it isn’t exactly new now, but there’s a newer type of noise reduction tool called a spectrum editor, which gives you — I’ll give you an idea of what I’m talking about — it gives you the audio in a 3-dimensional view.

So this is the view that everybody is used to seeing now of a waveform. A little jazz tune here. I just chose one channel unfortunately. There we go.

[jazz music]

Now as you can hear, that starts out with just straight noise.

[music]

Okay, and I’m actually going to zoom in right there, because that’s actually a good example of something. So here we have your average waveform. A spectrum editor looks like this. It’s a color editor, and it gives us a 3-dimensional view of the audio. Horizontally is time, right? We’re starting and it plays through horizontally. Vertically, we’re actually seeing frequency. So the lowest frequencies are down here, highest frequencies are up here, and I can see 100 to 20 is what we’re looking at right now.

We’ll get into all of this later in detail, but the color difference that you’re seeing is amplitude or volume. So you’re getting a 3-dimensional view of it, and as you can see right here, we’re actually seeing the harmonics of the guy’s voice if I zoom in on this. Once again, we will go over this in more detail, I just wanted to show something real quick.

Fundamental harmonic of his voice, first harmonic, second harmonic, etcetera etcetera, and you can see a nice big long flow of them there. So as the music plays, you can actually see his voice go, [sings melody]

[music]

And we got a little dropout right there I just noticed. We’ll fix that later on, but there’s a little drop out right there.

[music]

A little dropout there. So we’re going to use this for quite a few things. We’ve got some mouth pops and ticks I can see in the audio right here.

[song]

So this little guy and that little guy. So anyway, a spectrum editor allows you to see not only time and amplitude, but a standard editor only allows you to edit by time. I can edit left to right. This space.

I’m going to — right there, I just selected from top to bottom, all of the frequencies, but if I’m using my spectrum editor, I can actually draw a little box and only edit this area of frequencies. Remember, it goes from 0 up to 20kHz right here. So I can remove just one set of frequencies on the left channel or the right channel, and what a spectrum editor lets you do that’s pretty different from the standard editor is it lets you do some pretty amazing things like remove a cough out of a live performance, or a door opening while someone is doing a vocal. Solo the track, and obviously, you hear this door opening and closing really badly, and you can actually go and remove impulsive sounds like that pretty anonymously, like it never happened.

Depends on the problem and the tool that you’re using, but usually you can get it to sound like it never happened to begin with.

What I have here is a recording — it’s an interview that was done a couple of years ago by mister Bonzai who works for Mix magazine and a number of other publications doing photos and write ups and stuff, and this is the interview he did a number of years ago. He found a number of tapes, and our archiving department was helping him archive them, and there were a couple of them that had some noise, and some ticks, and pops, and clean ups.

So I think that might be a good thing to start with here is just kind of go through this and kind of look at some of these ticks. I can see right here we’ve got a tick if you look at that. It goes up and down, and that’s going to tick.

[sound]

That’s more of a thump. And this is where the spectrum editor comes in. When I look at a normal waveform, I can see that there’s something weird happening here. When I pull it open in the spectrum editor, I can see that it’s happening in the low frequencies. So this would be more of a thump removal than a tick at the very beginning here, if we were needing to get rid of that.

As far as how we’re looking at the audio, there’s a number of different ways of stretching. Is it going to be a linear scale, or a logarithmic scale? The more logarithmic that you get, the more low frequencies that you get. So you see that I changed that frequency scale, and now I can see that low thump happening there a lot better.

[sound]

Since this is really an interview and dialogue, that’s happening at — I can see the frequencies along the side here — it’s happening from around 90 to 100Hz and below. So that could even be taken out with a low cut filter or a high pass filter.

For the sake of what we’re doing here, I can adjust my screen a little bit so that I can isolate that a little bit. When you’re working with a spectrum editor, or even doing normal click and pop removal with this type of view, what you’re able to see and — these two sliders set my low amplitude range and my high amplitude range, and what you’re thinking of is if I have a volume meter like this, low amplitude, high amplitude, what do I want to see? Do I want to see all of that, or do I want to see this much of area, and where along this area do I want to see it? So I can actually go into the audio and get behind the loud stuff, and remove things that are behind the louder things. Okay?

So I just adjusted my view a little bit so that I could get that guy kind of isolated, that weird little thump.

Now if you notice this thump on the left channel and right channel is not identical.

[sound]

One happens before the other. So I’m going to isolate them. Let’s just do the left channel first. And we’ll grab our spectral editor and we just want to get rid of this guy.

Boop.

Alright, so we’ve still got this noise, everything there. That was really more of an example of how easily these things can work.

[sound]

That is such a weird buzz.

[buzz]

Okay. I want to just give this a listen real quick and see how many just erroneous pops and clicks there are.

[dialogue]

There’s a lot of lip smacks going on, and a big pop/tick right here. That sounds more like a lip smack too. I want to try just the automated overall and see what it’s going to do to this. So we’ve got random clicks going on. I’m going to put the frequency skew in the middle, and I don’t want my sensitivity too high, because I don’t want it messing with his talking.

One of the things that helps a lot with noise reduction is a lot of them give you the ability to hear the difference and only hear what’s going to be removed, so real quick I’m going to do that here with clicks only, and I’m going to preview it.

[clicks and pops]

So what we’re hearing right now is what’s going to be removed when I hit process.

What I’m really listening for there is to make sure that I’m not removing any words. Everything there just sounded like lip smacks and distortions. So if I process this now…

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We can actually watch it remove all of those here if I undo. Got on here, here, and a couple here and here, and when I redo, we can just watch them all disappear.

[dialogue]

Okay, so two things I want to point out about what just happened there. First off, the lip smacks were taken away, but not completely. Right here — I’m going to use the mouse — so right here and right here, I noticed that those lip smacks now sound a little more natural as opposed to someone right on a mic going [click] really super loud. Here it is cleaned up.

[dialogue, processed]

And here it is originally.

[dialogue, dry]

Music director. [laughs] We redo it.

[dialogue, processed]

And it sounds more natural, it doesn’t sound like he had the mic closer to him when he was smacking his mouth. Okay?

Now, I also noticed this tick right here. Now once again, I’m going to undo, and looking at this guy, that little blue area right there? It’s going to extend all of the way up when I undo.

Now, the reason it only removed the top half and not the little part at the bottom — we can zoom in on that — here it is redone. It didn’t remove this low frequency thump, but it did remove the tick up here. That would have to do with this frequency skew, and/or the click widening. Lower frequencies have larger waveforms, so it may need to be wider. I had the frequency skew right in the middle.

These “puh” lip smacks that he has go all the way down to 50 and 30Hz it looks like from what I’m seeing on the screen, so if I’m going to get rid of all of this stuff, I’m going to need the low frequency to be a little lower, and possibly the clicking to be a little bit wider.

Once again, if I redo that, we’re still left with this little thump here, and you can hear it.

[thump]

Right? So I’m going to undo that, and I’m going to skew down the frequency just a little bit more. Once again, I’m going to process the whole song, and — once again, I want this to be an iZotope tutorial, but one thing that iZotope is — to select the whole song, just double-click. But I’ve only selected everything in the screen, so if I now zoom out, I can see that I only selected that much, so it wouldn’t have done the whole song. So if you’re wanting to do — this is dialogue, not a song.

If you want to do the entire clip, you have to zoom out first to select everything. Just by double-clicking anyway.

So let’s process that with the click being skewed a little bit more towards the low frequency, and it should remove everything.

It still didn’t get that little thump there.

[dialogue]

I’ll be honest, I really like how it’s cleaning up those lip smacks. It doesn’t sound like the lip smacks are louder than the words he’s saying, but I am noticing a couple of thumps as it plays through.

This is one of the areas where it comes in really, really handy to have an excellent speaker system and — a full frequency speaker system that allows you to hear what’s going on down at 20Hz. I can hear that thump, not just see it. Not just see it on the screen, I can hear it.

[buzz]

Thump. So let’s go in and remove that thump. I’m going to zoom in on him just a little more. We can either take this frequency skew and widen the click, and I’m just going to select the area around that thump. Process.

Still not going away. Now, at this point is where I would reach for the spectrum editor and actually remove those frequencies and interpolate data back in, but I want to wait to get to that stuff, I want to just stick with the click removal right now. So on the de-click page, once again, we’ve got the regular de-clicker, we’ve got the de-crackler, and another one called interpolate, which is similar to what the spectrum editor program will do, and I’m going to go back into the view once again and adjust this a little bit more so that thump stands out alone. I’m going to select just the thump area, and in the interpolate, we only have one slider. Quality.

How much of it is it going to interpolate back? And by interpolate, what that means — I’m probably going to say that 100 million times by the end of this — I have this area here selected around the thump that we’re getting. What interpolation means is it’s going to look at the data on either side of that and redraw what should’ve been there with the offensive thing that I’m removing gone.

On the de-clicker, it doesn’t give us much control over that, meaning I do it and it’s going to interpolate whatever it interpolates.

When we get into the more advanced spectrum editors, and it actually allows you to choose where to interpolate the data from, whether it’s coming from above and below it, or from one side, or from the other side, you know what I mean?

The de-click interpolator in RX works similar. Notice how that just went away? So undo it, and look at the audio around it to. When we redo it, it actually matches the audio up to what was around it, because it’s using the audio around it to replace it.

So originally, what we had there was this.

[pops]

We de-clicked it with the automated de-clicking and got this.

[dialogue]

Whoops, sorry.

[sound]

So there’s one here, and there’s one here. Originally…

[sound, unedited]

There’s two of them in a row. With the automated de-clicker, we got rid of the click, but it left that little thump there at the bottom. Now, with the interpolator on the de-click algorithm, I was able to go in and remove that thump right there.

[noise]

Let’s do that to that second one there too.

So once again, originally…

[dialogue]

Automated removal and a little manual removal.

[dialogue, processed]

That big “uh” right there, I think this would probably be edited down to start right around here. So anyway, getting rid of those little pops and clicks, it’s not always just one removal of it. Sometimes, you have to remove it in pieces.

There’s a mastering engineer named Bob Katz who wrote a famous mastering book, and the way he put it was kind of removing layers of an onion. Sometimes, you remove one thing and realize that it was so loud, it was masking this other thing, so it can be a process.

A lot of people really hate doing noise reduction because of that, because it takes a long time. As you’ve noticed, I might run a process on something before getting the result you want, so it can be tedious. I enjoy it when I finally get that result and it sounds great.

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