I use audacity.Also, what editing software do you use?Many programs have audio noise reduction as a built in affect.
If yours does not, download Audacity and run your audio through that and apply the background noise reduction affect through there.
That should get rid of backgrounds hums and hisses like a fan or your a.c. or whatever.
I haven't thinkered around too much with audacity.Have you use the sound reducer of audacity? Mine works pretty well in removing the wind sound coming from my fans and the fountain in the garden![]()