Auto Profile in Noise Reduction?

Special Interest Groups Audio Processing
1

https://manual.audacityteam.org/man/noise_reduction.html

Re: This segment.

When using Noise Reduction in Macros the Noise Profile is captured as below.

I read that five times and didn’t come away with any understanding. Can someone describe the process and don’t use the words in that instruction block.

From memory, I didn’t understand it when that technique went into service, either.

Koz

2

It’s a bit confusing because it is 3 workarounds for 3 different use cases. Workarounds are necessary because the Noise Reduction effect isn’t really compatible with Macros. (There was a big update to Macros some years ago, that added support for nearly everything that Audacity does, but Paul was working on Noise Reduction at that time so it didn’t get updated for Macro support. Noise Reduction is the only “old style” effect remaining in Audacity.)

The main consideration regarding Noise Reduction in Macros, is that there are no settings available.
This means that if you want to use, for example, 6,6,6, then 6,6,6 must be the last used settings.
It also means that you must carefully manage when / how you get the noise profile.

The rules are:

  1. If Noise Reduction does not have a noise profile, running Noise Reduction in a macro will get one.
  2. If Noise Reduction does have a noise profile, running Noise Reduction in a macro will apply noise reduction.
    Thus, after a fresh start of Audacity (no noise profile exists), applying Noise Reduction in a Macro to a batch of files:
  • First file: Noise Reduction will grab a noise profile.
    • All subsequent file: Noise Reduction will use that noise profile to reduce noise.
      The same noise profile is used for all files.
  1. When applying noise reduction, the last used settings are used.

Personally, I find that the easiest way to use Noise Reduction in a macro (though not totally “automated”), is to manually get the noise profile and set the other settings before running the macro. That noise profile and those settings will then be applied to all files in a batch process macro.

3

First file: Noise Reduction will grab a noise profile.

And how would it do that?

Koz

4

It uses the whole of the first file as a noise profile (at least that’s my understanding)

Peter.

5

(at least that’s my understanding)

Yes, see, that’s the problem. You run into magic almost immediately.

I have done that myself. That’s one of the early ways to make a very, very slight dent in echo damage. No idea why it does that. I can conspiracy theory guess at it. It works best in bad echo situations because on average, the echo damage is louder than the show. The instant that average turns around, the repair stops working.

In this instance, if you add up all the tones and notes in a presentation, again on average, most of them are noise.

Being obsessive, I would have used the technology we use to measure noise and use that as a locator for a section of the show likely to be pure noise.

Koz

6

It’s not really magic.

Look at other macros, such as the included “MP3 Conversion” macro. The first step is “Normalize”. That works (on the entire imported track) because Macros automatically select the entire track on import. If that wasn’t the case, then the Normalize command wouldn’t work.

7

OK, forget the Macro.

In normal Noise Reduction, you select some “clean” noise from the performance and assign that the Profile. Audacity rips it apart, analyzes it, and configures tools to carefully remove that noise profile or characteristic from the show with the least damage.

Now do all that without the Profile.

Koz