I'll try to answer some of your questions but it is hard to determine where the noise is coming from if we can't hear it. Maybe you could post a song with the noise so we can try to determine where it is coming from. Also putting you system's data in your byline would help us.

1- the free Audacity and its plug-ins can do many things to a wav or MP3 including taking out noise. https://www.audacityteam.org/

2-Maybe but we would have to hear it. However it shouldn't be adding noise.

3-yes If the noise is not generated by your computer.

4-If the mic and fan are both on when you are recording then that could cause noise.

Have you tried to record anything other then BiaB? Try recording a youtube audio. Does it have noise? Doing this may determine where the noise is being generated, either by your computer and sound card or your recording.

A couple of last thoughts do you have a cell phone that is on near your computer or keyboards? We have had problems here with musicians having a live phone generating noise while recording and listening. Is your computer very close to your modem or router? That can generate noise also.

I hope this helps and good luck.

My wife and I decided to never go to bed angry.
We've been awake since last Tuesday!

64 bit Win 10 Pro, the latest BiaB/RB, Roland Octa-Capture audio interface, a ton of software/hardware