for something like this, I use a audio edit program such as Adobe Audition. using the noise reduction feature, make a “noise profile” of just the fan noise.
1. export wav & import into audio app.
2. in Audition, you only need to select 1/2 a second minimum of just the noise you want to remove from the wav you imported.
3. select “make noise profile from selection” & then save that profile.
4. don’t apply yet but close “noise reduction” filter after saving the profile.
5. select the entire wav then re-open the noise reduction filter
6. load the noise profile you saved earlier.
7. process with that profile tweaking as desired.
8. save processed wav. done!
hth,
Bill