I've used a few audio editors. Some were supposed to be good stuff! But, Audacity, impresses me with all the features it has. And, it's free!
When I first came across the noise removal feature in Audacity, I thought it was magical. I have been able to filter out all sorts of miscellaneous, extraneous and downright distracting background noise from my voice-over recordings. I know there is other software that does this, but... did I mention Audacity is free?
Here's the link, if you want to get Audacity for yourself and see what I'm talking about.
Oh! And here's my wee little tutorial. There's loads more I could tell you about the software, though I'll leave it at this for now.
By the way, choose the HD option and turn up the sound to better hear the noise removal tool's skills. Which probably means it's best viewed on YouTube and not here. Ah well.