How to eliminate noise with Dynamics processing?

Hi!

I'm trying to clean up certain audio recording, which has a constant backround noise from a working fan. I tried to use Hiss reduction and Noise reduction effects but somewhat cleaner noise still remains. I though maybe I could eliminate the noise at least on passages where it falls lower on certain amplitude since it's a class recording and the main thing is to be able to hear the speaker who is speaking quite loud. So even if the humming remains while the speaker is speaking, I would like to take it down on the pauses.

What settings should I use, I know it's the dynamics processing that can do it, but didn't find any good instructions of how to use it.

I include a snapshot to illustrate what I mean. In the red square is the noise I would like to take down.

Thank You for any help.

My regards,
Srivas

I've been so far presenting only questions here in this forum, so maybe it's my duty as a honored member to also present answers? But I underscore: since I'm not a technical maestro, my answers are just explanations of how I work myself. Not necessarily indisputable technical facts.

Srivas, if you only want to remove the noise from the passages/pauses where there’s no speech, I think one solution is to use the Effects-dynamics processing-noise gate presets @ 10 dB or @ 20 dB. But by my opinion it’s a little uncomfortable and difficult to adjust properly. It usually cuts off too much or too little, depending of the dynamics of the speakers voice. But if you have a long recording, and are in a hurry, this can be the fastest way. But if you have time and patience, you can of course mute all the passages manually.  Highlight the section and click Effects-Mute.

But…again by my opinion…it doesn’t sound nice nor natural, if it gets totally silent in the pauses. So I never use these options.

I do at lot of speech-recordings "in the field", with portable recording equipments, and edit and mix them in Audition 3. So I usually have a lot of undesirable backgroundnoises in the recordings.
The easyest way to get rid of them, is to use the Noise Reduction (in Edit view - Effects -Restoration - Noise Reduction (process)...).
First you have to find a long enough spot (2-5 seconds) in the recording with only the noise. After that you highlight the noisepart, open the Noise Reduction, and click on "Capture profile". After this the program loads the noiseprofile. Next: press the "Select Entire File". After this: Press the "Preview". Now, when you preview=listen to the entire file, adjust the "Noise Reduction Level" slider (from low to high) until the noise disapears.
When you're satsified, press "Ok".
Depending on the grade, level and type of the noise, it's sometimes easy to get rid of it, sometimes not. If you have to put the "Noise Reduction Level" slider up to 100, and the recording starts to sound metallic and robotical, and there's still noise, it's better to give up.

For cases like this, I usually separately record only the noise in the same environments in which I do the recordings. Then I have a long enough soundfile of only the noise. By using this file, I usually get better results with the Noise reduction process.
I open only the noise soundfile in edit wiev, hightlight the whole file, open Noise Reduction, press "capture file", and after this "save". I name it "xxx_noise" and save it somewhere where I can find it. After this I open the file I want to remove the noise from, highlight the whole file, open "Noise Reduction", press "Load from file", and search for that "xxx_noise"-file and open it. After it's loaded, I press "preview" and start to work with the "Noise reduction level" -slider again. This usually gives better results.
So Srivas, if you have the possibility to record only the fan sound, you can do it in this way.

If these operations still don't solve the problems, my third option is this: If I have the recording of the noise itself, I open it it edit view, click effects -invert. After this I have an inverted wavefile of the noise. I insert the inverted file in the multitrack view on track 1 and the file I want to remove the noise from on track 2.
Then by adjusting the volume of the inverted file on track 1 compared to the file on track 2, you can listen to how it effects/reduces the noise on track 2. I think this is principally the same thing that the "Noise Reduction" does, but here you can do much more adjustments, like using eq/compressors etc. on the noisefile to "finetune" the process. When your'e satisfied with the sound, make an "export audio mixdown" of the two tracks.   

Cheers!

Peter

Using the Companding preset in Dynamics effects will be slightly better since it won't reduce the noise to nothing but subdue it somewhat. You may have to fiddle with the values (or the graph) to optimize it for your audio. Looking at your picture it shows the noise to peak at around -12dB, so setting the Expand part of the curve to start around there.

Ok, thank you very much for these nice explanations! I'll try them out and let you know how it worked out.