Audio restoration and repair

Hi folks,

We’ve got a thread for mixing and mastering already, but I’m currently working on a long piece of field recording and that I took while I only had my zoom H1 and had to gain it all the way up :man_facepalming: . Now I’m in the position of working on reducing noise, cleaning up the recording, removing pops and noise, and getting gain corrected. I’ve never needed or wanted to ‘fix’ something in quite this state and I’ve got some questions!

I thought it might be nice to have a place to discuss the specific practice of doing restoration and repair work. (mods, feel free to merge this into something else if it seems appropriate :slight_smile: )

There of course so many great plugins and systems to work with these days, especially the izotope stuff.

I’ll kick this off with my current situation. I was recording singing ice up near Ely, MN. This is when cracks in the ice as it forming cause incredible reverberant sounds to echo across the lake. On large lakes it can be quite loud and sustained. In the Boundary Waters (one of the quietest places in the USA) it’s really amazing.

So, I made a long recording, but I only had my old Zoom H1 at hand during the trip. I’m now battling to get the audio into a usable cleaned up state. I’ve got access to the Elements version of the Izotope plugins. RX Adaptive noise removal is great and doubling it up has been even better.

I’ve found that there is a sort of oscillation in the track that I don’t even know where to being to address, somewhere around 40hz.

(you can x out of the dropbox dialog box and listen/download)

Here’s an excerpt of the track with the oscillations:
https://www.dropbox.com/s/0b0y8j8rnh5sy3z/osci_Marker%2002.wav

and an excerpt of the singing ice for those interested:
https://www.dropbox.com/s/n4xa9tp8t14jf9p/sing_Marker%2001.wav

I would be very grateful to hear any thoughts or ideas about cleaning up that thumping and any strategies you might have used to get noise like this under control beyond tossing some RX plugins over top!

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I think noise reduction has become a standard part of recording capturing sound. That said, recording very dynamic or quiet sources demands high quality mics and preamps. The H1 is a nice portable recorder but sounds like these make a good task for a Sound Devices unit.

  • high pass filtering is quite standard on recordings like this, especially when bass isn’t the most important part of the material, otherwise that rumble consumes all your amplitude range. If you don’t need it in the mix, just highpass it.
  • RX is fine but maybe you do want a bit of noise, maybe a 4-5-part multiband gate expander sounds better in the mix than spectral noise reduction.

So much of this is trial and error. The brain does such sophisticated noise reduction, it’s hard to match.

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For the low freq blurps: what about just a highpass @ ~20hz? Looks like those artifacts are all well below 20hz, you could probably roll off even below 5hz or something if you want, if I use a huge analysis window I don’t see much of any energy in the artifacts above ~4hz. Here’s with a 8192 frame window, at 32,768 you can see the rolloff around 4hz better though…

Awesome recordings btw!

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I’ve done it before, but just felt like this was a good thread to evangelize the acon digital restoration suite again because I feel like they are a bit hidden out there. If (like me) rx advanced is a bit steep (either in terms of price and/or learning curve) and the waves plugins run terribly on your computer, and the rx light versions aren’t doing it for you, check those out. I use the denoise all the time when I mic something. Recently have been experimenting with declick and it’s pretty incredible if you want to get clicks out of chopped sampling/granular stuff or just background clicks from noisy circuitry.

Also, on the non gear side, I think audio restoration for creative use is definitely an art. It’s one of those things where a little goes a long way, and a lot of times you want to leave some of the artifacts because the character actually adds and does not detract from the actual listening experience IMO.

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I’m by no means an expert in this, but one thing I’ve found helpful for periodic thumps and the like way down low, there, is that just straight up copying a chunk of that frequency range from a nearby section of the audio file and pasting it over the offending part can go a long way in dealing with stuff like this – sometimes more so than brute force de-noising, de-wind, etc.
More specifically, in RX, just use the rectangle or lasso tool to draw a shape around the artifact you want to remove, than pull that shape over to a clean part of the sound nearby, copy, then paste it back over to cover it up. (which, I’m assuming RX Elements lets you do this, right?)
Of course it takes some finessing sometimes, and YMMV depending on where the focus is in the overall frequency spectrum, but you can get away with a lot this way.
Or, yeah, as other posters said, just rolling off the low end works too!
Great recordings, by the way–

[edit: hit cmd+enter by accident before finishing]

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I’m doing little bits of repair and restoration most days in mastering, it’s the first thing I’ll do to tracks after the first listen, if needed. RX Advanced all the way here, for about a decade now. It’s saved my life many times and paid for itself multiple times over. It can work miracles.

Although I’m also interested in checking out the Acon Digital Restoration Suite at some stage, as it’s cheaper and updated far more often.

Restoration Suite | Noise Reduction Plug-ins (acondigital.com)

Acon Acoustica premium edition comes with the restoration suite and it can do some really trick stuff with the spectral editor:

like removing unwanted aperiodic sounds while leaving the ambience @bmoren

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Yeah that was the puppy I was thinking about, not just the suite. I need to dermo it, would be good to switch if it out-performs RX as it’s cheaper and just a small dev who seems to care greatly about his software, and updates it regularly. iZotope do a bugfix release with a couple of extra features (rarely needed by me) every year or two and charge me $400 for it…

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Wow, as much as I love the plugins, did not know about this standalone tool. I’ll definitely be giving it a trial whenever I come across a situation where I need that extra spectral horsepower.

Slightly off topic, but on the subject of audio restoration for creative use, the first few minutes of Daniel Menche’s Kataract (a harsh noise album made from waterfall recordings) are very interesting. As I recall, Menche put some noise-removal plugins to work on some waterfall recordings, which obviously sound quite a lot like whiteish noise. So what we hear is what the algorithm thinks is ‘behind’ all that noise: a kind of distant wind howl, as it turns out.

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Ah cool, I was actually exploring that technique last week. I used declick on a recording with very high threshold and solo’d the removed “clicks” (also duplicated the recorded track and slowed it down by four times with ableton’s beats algo to create something sort of beat repeat-like). TBH, I think the track I came up with is pretty uninterresting especially at the length it is, but I do like the noise texture that resulted from the technique and will revisit again.

https://drive.google.com/file/d/1PB9nIvyzsJLQjlKK6dFKaKWT9z_7fpYQ/view?usp=sharing