Using Audacity to remove PC fan noise from mic in real-time?

My computer fan makes a lot of noise which is very easily removed from a recording using Audacity. I would like to remove the noise live while I use my microphone to talk using other programs (e.g. Skype or an online game). Is that possible?

Someone said they achieved this using Adobe Audition and Virtual Audio Cable but the video describing the set up has been removed from YouTube (it was posted a long time ago).

Audacity is a post-production editor and does almost nothing in real time.

Many computers have real-time noise-suppression as soundcard “enhancement”.
For people recording music with Audacity we recommend such enhancements are turned off , but in your case if your sound-card has noise-reduction turn it on.

NB: the noise-suppression in the sound-card is compeletely seperate from noise-reduction in Audacity.
You don’t need Audacity to use it.

What about recording the sound, making it into the antithesis and then playing that constantly through the mic so it cancels the fan sound?

[My mic uses USB and doesn’t have the enhancements such as noise cancellation]

Unfortunately doing that would not cancel-out the sound.
Even if the unwanted noise was a constant tone of constant volume , (rather than unpredictable random noise) , the phase would have to match for destructive interference.

Red line is the result : it only goes flat , (i.e. silence) , when when red and green are anti-phase.

Turbulence in the moving air means the sound will always have a random quality and won’t cancel even if you do manage to get it close. Try it. Record some fan noise and open it below a voice recording you already made (again, Audacity doesn’t do anything live).

Select the whole track by clicking just above MUTE.
Effect > Invert.

Now use the volume slider on the left of the track and the Time Shift Tool (two sideways black arrows) to push the track around. See if you can get it to cancel.

Do Not move the microphone or anything in the room during this experiment. Any movement will affect the acoustic signature and kill the cancellation.