Noise Reduction Question - Likely a dumb question but ....


So I’m currently digitizing an old cassette tape with back-to-back audio recorded birthday messages from the past.
There’s a lot of buzz/hissing noise for which NOISE REDUCTION has been very effective … in most cases.

These are the recommend steps that I go thru.

  1. Select a short 1-2 second pause in a person’s message where it’s silent but noise is audible
  2. Go to NOISE REDUCTION and click on GET NOISE PROFILE. This then closes out that setting pop-up.
  3. Then re-select the entire section of that message to apply that noise reduction profile
  4. Go to NOISE REDUCTION again and this time, hit OK
  5. I repeat these steps for sections at a time as the recording is a patchwork of different people at different times so each section has different background noises (and when I say background noises, I don’t mean cars, wind, and such… just the basic hiss/hum due to the acoustics of the room and how close they were to the mic when recording)

Now. I always found it kind of funny that the three manual settings for this effect (level, sensitivity, band) do not change depending on that specific noise profile captured… but I just assumed that it was temporarily stored as the next profile to be applied. A bit like how basic CLIPBOARD works.

Well after hours of effort, I decided to play with the manual settings on some sections that the above steps were not as effective. That’s when I realized thru trial and error that the GET NOISE PROFILE step doesn’t seem to be doing anything?!?! Theoretically, if I compared 2 trys of step 1-5 on the same audio section but in each attempt, have the manual settings at different levels prior too step 1, the end result should still be the same, right? At least that’s how I understood the purpose of the GET NOISE PROFILE step.

However, this is not the case. Can anyone shed light? Did I misunderstand? Did I miss a step? or is there an error in my setup somehow?

IMO one should increase the level on noise-eduction rather than apply it twice.
(Each application of noise-reduction adds computery processing artefacts)

Thanks for the reply! I agree with your response (if I’m understanding you correctly) but perhaps you misunderstood my mention of the TEST.
Let me rephrase it this way:

I was under the impression that getting NOISE PROFILE of “silent” portion of your audio allows Audacity to analyze and create a custom setting to apply noise reduction to best remove that profiled noise from the applied section.

And so as an A/B comparison test, I took the same stretch of audio and went thru steps 1-5 (as recommended by various sources online) but in CASE A: before step 1 of pulling the noise profile, I had manually set the 3 settings relatively low. And in CASE B, I had manually set the settings at different, higher levels before pulling the noise profile.

Since both cases are pulling from the same audio clip untouched, I assumed the custom noise profile pulled would also be the same and so when applied in either case by going thru steps 1-5, the end result would be the same. But they are not. They are different based on my manual settings – which makes me question what the GET NOISE PROFILE step was for?

Either I am not properly capturing or not properly applying the captured noise profile with the steps I described (which I got from several sources) OR that those steps are no longer valid and are outdated OR I completely misunderstood the purpose/application of the GET NOISE PROFILE step.

Does that make more sense?

Did you change the “manual settings” back to some standard setting before doing the noise reduction step? If not, what you’re hearing is the difference that the 3 manual settings have on the noise reduction step, not on the get noise profile step.

– Bill