Noise reduction tool settings question

Hi…I’m converting old audiobooks in cassette format to mp3’s. I’m having a problem with aggressive background noise…not the whole time, just a few seconds here in there. It rather sounds like a jackhammer or machine gun going off …but as I said…just a few seconds here and there. On audacity the blue lines shoot from bottom to top until it passes. My question is this…I’ve learned about the noise removal tool but I have a feeling this isn’t going to be fully removeable. But I dont understand the settings on the tool…there is a place for a number next to noise reduction, sensitivity, frequency smoothing, Attack/decay time. For maximum results, how should those boxes be set? Juls

Rather than using noise reduction, (which will not remove gunshots), could momentarily turn down the volume using the envelope tool

If there are a lot of gunshot-type noises, try this Pop-mute plugin which will quieten all of them automatically, (rather than individual manual correction with envelope tool).