Noise Reduction in Chain (not working) [SOLVED]

Audacity Help Forum macOS
1

Hi forum,

Here’s my version number for both OS and Audacity:

Audacity 2.1.0 (latest)
Mac 10.10.3 (Yosemite)

I’m trying to apply Noise Reduction as the first effect on a chain. I’ve tested many different methods according to the methods found on this wiki: http://manual.audacityteam.org/o/man/noise_reduction.html.

  • If a Noise Profile exists, that Noise Profile will be used. It is often best to capture a suitable Noise Profile before running a Chain.
    If a Noise Profile does not exist:
    • If the Chain is applied to the current project, the current selection is used to create the Noise Profile. Therefore, other effect commands in the Chain will also only apply to that selection. If an export command is added, the entire file will be exported.
  • If the Chain is applied to files, the first file (all of it) is used to create the Noise Profile. It may be useful to prepare a file containing a suitable Noise Profile and name it so that it is alphabetically the first file of those to be run in the Chain.

Setup for all repro steps below: four WAV files in a folder, the first one alphabetically is 10 seconds of near silence copied from one of the other three clips. Also the last effect in my chain is a WAV export.

Apply to Files, Repro Steps:

    1. Open audacity
  1. “Apply chain”
  2. Select four WAV files

What happens: transforms all four WAV files according to other chain effects (e.g., normalization, equalization, etc.) but does not apply the silence recorded in the first file. (Not sure this is a good implementation anyway, because the first file is processed according to the other effects so it’s ambiguous whether the profile is the processed near-silence file or the unprocessed one.)

Apply to Files with Noise Profile, Repro Steps:

    1. Open audacity
  1. Open one of the WAV files
  2. Grab 10 second profile (“Effect” > “Noise Reduction” > “Get Noise Profile”)
  3. Close file (tried both saving and not saving audacity project file)
  4. “Apply chain”
  5. Select all the WAV files assuming now the Noise Profile is saved (anyway to test this? allegedly as long as you don’t close Audacity the profile remains.)

Note: I’ve also tried using the “Get Noise Profile” button on the “Edit Chain” parameters menu.

What happens: transforms as above but no noise reduction.

Apply to Current Project, Repro Steps:

    1. Open audacity
  1. Open one of the WAV files
  2. Grab 10 second profile (“Effect” > “Noise Reduction” > “Get Noise Profile”)
  3. “Apply chain”
  4. “To Current Project”

What happens: transforms as above but no noise reduction.

Apply to Current Project, No Chain:

Just to be clear and assure you I know how to use this effect, if I apply it manually to a file it does work. I can tell because of the “L” and “R” output meters are zilch.

Anyone have luck with “Noise Reduction” in batch processing chains?

2

if I apply it manually to a file it does work. I can tell because of the “L” and “R” output meters are zilch.

That usually means you’re overprocessing just to throw mud in the game. That’s a good way to make the performance sound funny. Noise reduction affects everything and it’s your job to set the balancing act. It’s not a Howitzer just aimed at noise.

Koz

3

Testing on Windows (I think Steve has tested on Linux before) it seems to be doing as you quote from the Manual.

I’ve looked carefully at the waveforms and in Plot Spectrum, subsequently applying the same noise profile to the originally exported file as was applied to the files exported by the Chain, and the results seem identical.

Are you following our general recommendations about the order of applying other effects with Noise Reduction:

  • Amplification or normalization may be done before or after Noise Reduction.
  • Do any Notch Filtering or Click Removal before doing noise reduction.
  • Do any compression or any other effects not mentioned above after doing noise reduction, not before.

I suspect the real problems are not being able to tweak the Noise Reduction parameters when you edit the Chain unless there is already a Noise Profile, and having no way to save and retrieve noise profile audio files within the effect.

Gale

4

Gale,

So hmmm, it…uh…works.

I’m a developer too and I hate hasty bug reports so I thought I was being thorough with that one. I can’t explain why it wasn’t working yesterday – most probably something stupid on my part, but I deleted my chain and rebuilt it so perhaps it was something I was doing to my audio after Noise Reduction. I will do 50 Hail Mary’s for wasting your time.

Also, I donated a small token sum. Currently I’m burning through my savings on a project, but just want to say thanks to you guys for the awesome product.

Kyle