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So I have an entire mountain of dialogue that has rain noise all through it.

There is also a good deal of clipping throughout the movie.

Does anybody have a clue about how to remove the rain splatters in particular?

Thanks!

EDIT:: Also, can anyone explain the aliasing sound you get sometimes in the NR process? I'm using Izotope

Do you have a online site to learn about RX2?

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Try Izotope RX. Use the denoiser to remove some of the broadband noise, and ride the volume, so you decrease the volume between the words. You can remove some of the splatters with spectral repair. Make a mono background atmosphere which sounds dry, which you can use to mask the rest of the rain sounds.

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  • when I do that, it gives me a lot of nasty digital clipping/anti-aliasing sounds and i cant use the denoiser without introducing it – Chris Feb 20 '11 at 18:40
  • Normally you can remove 6-8 dB of broadband noise without any artifacts in RX denoiser if you run it in C or D mode. If you get a lot of clipping, you probably have to run it through the declipper first, and then use the denoiser. – Morten Green Feb 20 '11 at 19:34
  • Thanks. I'm still not sure how to remove the splatters using spectral repair, can you elaborate? – Chris Feb 20 '11 at 19:41
  • Are you using RX as a plugin on a track or in audiosuite? When working with noise reduction, I always use audiosuite to print the changes to an new sound file and keep the original sound muted on another track. This way I can always go back if I accidentially overdo the noise reduction. – Morten Green Feb 20 '11 at 19:42
  • You can probably see the splatters as vertical stripes in the spectrogram in spectral repair. You can mark up just this vertical stripe and attenuate/remove it. I guess there are a lot of those, so you'll probably have to live with some of them, but can mix your way out of a lot of them and try to mask them with other sounds. Is it supposed to rain in the scene? – Morten Green Feb 20 '11 at 19:45
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I second (or third?) the gentle RX and volume riding. Also, Waves C4 set to the noise reduction factory setting, if you have it, is very helpful to introduce after the other noise reduction.

Also, can you use rain in your atmos tracks? Or some other kind of atmos that will help mask your noise.

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  • Yes i used some atmos for masking, thanks. – Chris Feb 21 '11 at 2:07
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Are you refering to the smearing sound in NR? That's normally when you push it a bit too hard. Perfect FFT and FIR algorithms don't exist; plus, subtracting noise heavily may create an inverse print of it on the useful signal. It's all a big tradeoff...

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  • The smearing yes. The digital sounds when you push it too hard. – Chris Feb 20 '11 at 19:44
  • As few as 6 bands on a multiband expander are enough to get the smeary feel. Try it. With RX you're talking no less than 200 bands... – georgi Feb 21 '11 at 2:14
  • Would love to find a real manual for Izotope – Chris Feb 21 '11 at 4:08
  • google.com/search?q=restoring+audio+izotope+rx – georgi Feb 21 '11 at 15:24
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I will offer potential elements of answer concerning aliasing (as an artifact from over-processing a source signal). It is bound to be a phenomenon occurring independently from the process you are trying to apply. Any plugin might generate some aliasing or artifacts in a broader sense.

As you process a source signal, the processor reshapes the waveform using quite simple maths (in the end, all the maths electronics can do is add or divide). Basically, a processor adds to the original signal the statistical signal that it thinks will compliment best the component you're trying to isolate.

In the case of BNR, it calculates a statistical image of the noise and will smudge the waveform where it finds that the original signal features a "picture" of the statistically accurate noise. The more you push it, the more it's going to smudge the waveform and it'll start critically eroding the signal you're trying to focus on and listen to.

In effect this creates irregularities in the flow of waves that, when played back, are not natural sounding. Aliasing is merely an artifact that generates a particular sound; as it happens, the artifacts are organized in such a way that you seem to hear this tin foil kind of sound (that's the most obvious example, although aliasing can exist at any frequency although I have reasons to believe it'll always appear gradually from the high-end of the spectrum).

As a final note, the aliasing effect also happens when you record a sound. You may have heard of the "Nyquist frequency" or "Nyquist theorem". It's simple physics: to capture a certain frequency correctly, you must sample its waveform at least twice per cycle. Say you can only record with a sample rate of 20kHz, you'll be capturing frequencies just fine until 10kHz, only you won't be able to reproduce higher frequency correctly. I'm even gonna draw a diagram that'll explain this simply :)

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