Sometimes when I record audio or video with my laptop I get some machine noise (a low volume, sort of high pitch hum) in the audio.   GarageBand can do a lot to tweak audio (iMovie can't do much except normalize the clip volume and adjust overall volume), but Audacity is supposed to have a noise removal function.

Problem is, when I'm working with an audio file in Audacity and I click "Noise Removal" (under "Effects"), it tells me to select a few sec. of just the noise -- so they can analyze it - and then to click "Get Noise Profile." That's Step 1.   

OK, so I figured out how to select a short segment with just the machine noise. I did that and even copied it, in case I needed it.   Then I clicked "Get Noise Profile" and the program seemed to be doing something ("Creating Nose Profile"), but I couldn't see the noise profile or any info on its variables.

Step 2 says "Select all of the audio you want filtered, choose how much noise you want filtered out, and then click "OK" to remove noise."

It then asks me to decide the following (insert numbers or leave the default ones):

Noise reduction (db) -
Sensitivity (db) -
Frequency smoothing (Hz)
Attack/decay time (secs)

The program does not seem to tell me what levels should be punched in, but even if I go with the preset levels, when I check the previews on noise removal, nothing seems to have changed.   In fact, I can't seem to find anything that reduces, much less removes, the machine noise.

Does anyone have experience with using Audacity to remove noise?   The "Help" instructions are quite unhelpful. They don't tell you any more than what the pop-ups tell you when you use the drop down menus and click on things like "Noise Removal."

I'd really appreciate any information or suggestions if you know how to do this.

Thanks,

Genie