Join Scott Hirsch for an in-depth discussion in this video Philosophy and workflow of repairing and enhancing audio, part of Repairing and Enhancing Audio with iZotope RX 4.
- So you can watch amazing isolated examples of how iZotope RX modules can seamlessly fix audio problems. But in your own experience and with your own files, before you fix anything, you have to first learn how to identify what the problem is, before you can start repairing it with the modules. In this movie we'll discuss how to identify common audio problems, and we'll explore iZotope's suggested flowchart on what order to solve the issues with. Now to see a comprehensive range of problems you might encounter, I prepared this rxdoc with a bunch of samples.
Notice I made the use of markers across the top of the screen here. These are examples of selection based markers, and you can make any marker of your own. If you wanna make a single marker you can just click in anywhere in the timeline, open up the Markers and Regions window and here we can see all the markers I've already made. But if I wanted to add a marker, say at this location, I can click Add, and then I can name the marker.
I can also make a selection based marker by creating a selection, and then clicking Add, and then I can make a selection based marker that will stay there. And as you see, you can add comments or anything else that you might want to add that will show up in the Markers and Regions window. Now to remove these I can just select them and remove them. The other cool thing about the Marker and Regions window is that I can jump to any marker by clicking on the little yellow icon.
So if I wanna go to the Clicks and Pops selection, I click there and it automatically selects the audio, and then I can play that audio. - Ladies and Gentleman. - I can also click just on the little triangle which is basically a play button, and it'll play from that location. - Blast of. Blast off. Blast off. Blast. In this case it's looping, because I have the loop button turned on. So that's how markers work, and again I've made a whole bunch of markers across the timeline so we can quickly jump to these all examples of audio problems we might encounter, and we'll talk about what modules we might want to use to address these problems.
So let's start at the first one, it's called Clipped. And I can zoom in a little bit on that selection, over here on the left, I have clipped audio. Clipped audio is the name of audio which has overloaded the input of a mic, a recording device, an interface, etcetera. If you digitally clip, or you overload the input, what happens is the waveforms get basically squared off. And if we zoom in a little more, we can see the top part of these waveforms has been chopped off, and that's essentially why we call it clipped.
And here's what it sounds like. - Welcome to kiapics.com, the number one image hosting site on the web. - So over here, it's not clipped. The first part is clipped, and you can hear a kind of crunchy character to that audio. - Welcome to kiapics.com. - Now luckily we can fix this really easily with a module called Declip. So, if I open this up, we can see the Declip module and it'll essentially find where the audio is clipped, and restore it. Now, don't worry, we're gonna go into how to use all these modules as we progress in this course.
For now, I want to concentrate just on identifying the problems and talking about which modules we'll use to solve the problem. So let's move on. Let's go to the next example I have, which is called Distortion. And I'll zoom out, and I'll zoom back in on the Distortion section. So now, distortion at first might sound like clipping, but if you look at the waveforms, you don't see any clipped waveforms. What we do hear is some distortion, and let me play it for you.
- Blast off. Blast off. - So that doesn't sound perfectly natural, it sounds like there's some kind of build up of frequencies going on within the spectrum. Now to fix this, there's a couple of modules you can turn to. If you're an advanced user, you can use the Deconstruct module which lets you actually reduce Noisy gain versus Tonal gain, which can help extract some of that frequency build up. If you don't have iZotope RX 4 Advanced, you can use Spectral Repair to look at and analyze the audio and find where those frequency build ups are and lower the volume of the frequency build ups to make a distorted passage a little bit more natural.
Okay so, moving on, we've got Clicks and Pops. This is pretty obvious in terms of the name. Let me just play it for you, and we can hear some clicks and pops. - Ladies and gentlemen, we are approaching Mars' lower orbit. Fasten your seat belts and prepare yourself for atmospheric reentrance. - Now, you heard those little clicks and digital glitches in there. Digital clicks and pops like this can be caused by digital clocking errors from a digital recording device that's something's wrong going on, bad sample rate perhaps, it's not synced to another device.
It can happen if you have bad digital cabling. It can also happen in the analog world if you're working with audio from vinyl records, for example. You're gonna have some clicks and pops because of the dust and possibly scratches of the vinyl records. Luckily, to fix any kind of clicks and pops like this, we have a Declick module. And the Declick module, let me just return it to it's default setting, has three tabs. Declick, Decrackle, and Interpolate. And a combination of one or more of these tabs, can really help isolate and take care of a lot of the clicks and pops we might encounter.
Okay, moving on, I have an example called Crackle and Mouth Noise. Now if you've recorded any VO recording, or any close-up vocal performances, you might be familiar with mouth noise that you can hear in that recording. Let me play an example for you. - Finally, click the upload button and you're ready to share your image with the world. Finally, click the upload button and you're ready to share your image with the world. - Okay it sounds pretty good, but we do hear a lot of that sort of clicky, crackly mouth noise, and we could make this a lot cleaner.
And we would do that by using also the Declick module, specifically the Decrackle tab of the Declick module will help us take care of any kind of mouth noise problems like this. Okay moving on, I have an example called Amp Hum. Now hum is a specific kind of audio problem where you have a continuous tone running throughout your audio, and there's a couple of characterizations of it. In the first example here called Amp Hum, it's a guitar playing through an amp.
And if you've ever recorded amps before, you've definitely heard that they can have some audible hum. Let's take a listen. (electric guitar) So hum can come through cables electrically, or it can just be present in a room if, for example you forgot to turn the refrigerator off. It can be heard audibly as a low frequency tone, and it's usually based at either 50hz or 60hz, depending on whether the recording was made in Europe or North America, because of the different way the electricity works in both places.
Here in this example, it's related with an electric guitar amp, and it's at 60hz. And you can see though visually, the bending across the bottom of the spectral readout of this clip that it actually occurs below the usable audio signal of the guitar, which is happening above that area. So for situations like this, the Remove Hum module works really well. You can basically give it a base frequency and we can add in basically EQ filters that have very tight response curves to deal with some of these problems.
And it's a very effective way to get rid of hum, like we're seeing here. But the other type of hum that we might encounter, I've name In Spectrum Hum. So let's take a listen to this, and see what the difference is. - Fasten your seat beats and prepare yourself for atmospheric reentrance. - So this clip also has a hum, but you can see visually that the bands of the hum extend well up into the area where the voice is. So for this type of audio problem where the hum is sharing frequencies with the audio you want to keep, you probably won't have a ton of luck with the Remove Hum.
For this type of audio problem, you'd want to turn to the Denoise module. And the Denoise module, if you can get an isolated example of the hum, you can learn the hum and then you can work to remove it from the area where the voice is, where the frequencies of the voice are without altering the voice. So that might be a better way to deal with that kind of problem. Okay next we have an all too familiar situation. I'll just play it for you and you can hear it for yourself.
- 10. Nine. Eight. Seven. Six. - Yes it's cell phone interference, so if you have a cell phone too close to the recording device, you can get some intermittent blips and bleeps into the recording like we have here. Luckily for this type of problem, we can actually use a preset in the Declick module. If you go up here to Presets, there's actually one specifically designed for this type of problem. And that'll take care of most of the problem, and then the rest of the cell phone clicks and buzzes can be taken care of with the Spectral Repair module.
Okay, the next selection is something we call broadband noise. This is what happens when you've got noise problems, not hum based noise problems, but just broadband, meaning they're happening across all of the frequency spectrum. Something like an air conditioning or a fan is a good example of broadband noise. Let's take a listen. - Fasten your seat belts and prepare yourself for atmospheric reentrance. - That air conditioning unit that we hear in that recording might have some hum components, which you can see banding across, but you can also see that the noise problems extend as just broad sort of, scattering of frequencies that exist all up into the audio spectrum.
Now to take care of this kind of noise, we'd also turn to the Denoise module, and we can try the Spectral Denoise. There's also one tab of the Denoise module that's specifically made for dialogue based denoising. So that might be a good opportunity since this is dialogue, it's someone speaking, we can try out in this case the Dialogue Denoiser. Okay, our next example is something we call intermittent noise problems, so take a listen. - Everything that I look for in life, from family to-- - Just move this. - everything that I look for in life. - So here I'm gonna zoom in a little bit.
The voice sounds okay but you can hear intermittent noise problems. Which in this case, come as the sound of birds. - Everything that I look for in life, from family. - And you can actually see where the birds occur, occurring here and here, and watch those areas as we play it. - Everything that I look for in life, from family to. - So anytime you have this kind of intermittent problem, maybe it's a chair squeak, maybe it's someone coughing in the background, or in this case, birds. You can deal with these with the all powerful Spectral Repair module, and you can actually select those areas and work to either Attenuate, Replace, or Pattern replace those types of problems very effectively.
And that's one of the most powerful modules in iZotope as we'll come to see. Okay the next problem we have, is called Dropout. Dropout is characterized by short periods of missing audio. Dropouts can be the result of a digital glitch, a bad RF, bad radio frequency from wireless lavaliers, that's a really common place you might have dropout. Even bad tape in the analog world. So let me play this and we can see where the dropout occurs. - Ladies and gentlemen, we are approaching Mars' lower orbit.
- Okay so right there, I zoom in really close, right where he says Mars' lower orbit. - Mars' lower orbit. - Okay, so you see there's a missing chunk of audio right there. That would be a dropout. We can also deal with dropouts by using the Spectral Repair module. And here we can use either Replace or Pattern to find and isolate audio that's like this missing area, and interpolate and fill in that area.
And for our last example, we have a recording with too much reverb. Now usually people think of reverb as a good thing, but let me play this example and you can hear when we might not want reverb. - Too much sugar dehydrates you, and robs your energy when you need it most. - So the space of this recording is interfering with the intelligibility and even the mood of the recording. And removing reverb from an audio clip like this, is kind of like a holy grail of audio restoration. It's maybe the hardest thing to fully remove from audio, since the room or the surroundings we want to remove are so blended in with the audio we want to keep.
For this type of problem, RX 4 Advanced users can turn to the Dereverb module, which basically analyzes a clip of audio like this, and finds out where it can sort of get rid of, or dock the reflections, the unwanted reverb. It's a very powerful tool part of the RX 4 Advanced Suite. So that's a pretty comprehensive list of audio problems you might encounter in the world. But many recordings have more than one of these issues going on. So in that case, where do we start, and what order do we process the problems in? Luckily iZotope in some of their documentation made a very handy flowchart of how to diagnose and what order to diagnose issues in.
So here is a flowchart, a sequence of steps, questions you can ask yourself basically, as you go through. The flowchart starts with the question, Clipping, and know we know what clipping is, right? So is it clipping? And the way this works is, if it is clipping, you would go to these modules. Start with the Declip module. If that doesn't work, go to Decrackle. If that doesn't work, go to Deconstruct. So you can follow this flowchart around, and you just basically ask yourselves the question. Is clipping your problem? If not, go on. If stereo file with stereo noise clicks is not the problem, you go on.
And so basically this gives you a really nice flowchart with sort of suggested order and way to diagnose audio problems. A very handy thing, you might want to print it out, and keep it next to your work station if you're doing a lot of work in RX 4. So even though we've identified specific modules for specific problems, I want to point out, that even with all this technology, there is no one-click magic button or silver bullet that will fix all the problems with your audio. You can use these modules, but use of them requires very exact and skillful selection techniques.
That it requires accurate settings, and this is the main part, a lot of trial and error on your part to make even small improvements. So there, I said it. iZotope RX can help repair your audio and make it better. There's no application under the sun that can fix everything perfectly all the time. It's gonna require you to use a lot of your listening skills and a fair amount of time to try things, undo them, compare things, try some modules against other modules and see which one works better, etcetera.
So right now I'm working on a time machine that allows us to go back to the date and location of recordings when they were made, and do things like turn off the refrigerator or dampen the room, so it's not so reflective. But until I get that done, iZotope is the best tool we have to deal with some of these audio problems we're going to encounter in our recordings.
- Exploring the workspace and workflow
- Processing files
- Cleaning audio
- Removing noise
- Working with a DAW
- Cleaning up noise in music and field audio
- Utilizing EQ Match and Ambience Match to fill gaps and match audio
- Time-stretching and pitching audio