What you are attempting to do requires a bit of work and then some luck.
It sounds as though you have an Audio Clip with both background noise and possibly music, plus dialog. You wish to remove just the dialog in a particular spot, or spots. Is that correct?
If so, then in an Audio editing program, like Adobe Audition, you can possibly extract the ambient sound/music with a Karaoke Effect, or with the application of EQ. This will yield a separate file with hopefully just the background and music, and no dialog. In a Multi-Track Session, place both files on a separate Track. Find the point where you wish to remove the dialog. Here, the workflow might differ, but I'd Cut out the dialog at that point, leaving only the Karaoke Track. To clean things up, when I had done this for each offensive passage, I would go to the Karaoke Track and do just the opposite - Cut out all that was NOT underlying the offensive passages, but leave a bit of that Track before and beyond the deleted dialog. Then, I'd add a Cross-Dissolve for Constant Power to those Karaoke segments to "ramp" the Karaoke Track into the mix, as it will never be perfect, and one wants as smooth a transition, as is possible.
Now, one can do this in other audio editing programs, that offer Multi-Track editing, and also VST plug-ins, or install with Effects like Karaoke and/or Parametric or Graphic EQ's. You could explore the great, free audio-editor, Audacity, and Google for VST's that will enhance its capabilities. Be sure to read the Help files on Audacity, as one does need to do a few things in setup to allow the addition of more VST's.
The work will be with the Karaoke (or similar) Effect, its result and also the frequency ranges of the speaker. That is where the "luck" comes in. Much human speech can be EQ'ed out, or at least greatly attenuated. Now, if you have a crowd talking in the background, or similar, and wish to retain that, all bets are off.
Also, if you only have ambient sounds, and no music, behind the speaker, just find segments of that ambient sound, where the speaker is not talking, and use that to "patch" where you cut out the dialog.
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Here is a freeware Karaoke Effect program. I have never used it, as I do my work primarily in Audition and would use Center Channel Extractor (perhaps shifting Phase 180 degrees) to create a Karaoke Effect. Cannot vouch for this program, but it is free, and sounds like it would do exactly what you want.
Thanks, that was a great help! One question, what are VST's?
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Glad that it was helpful.
VST's (Virtual Studio Technology) are basically plug-ins (usually in the form of .dll's), that can be used in audio-editing. Some work in some programs, and some in others. A few will keep programs from even loading, it they cannot work with them, and they cause an issue. This Wiki-pedia Entry will give you some background.
VST's can be "instruments," effects and a lot more. One common type is equalizers. One common type that cause issues with programs, other than the ones that they were written for, are the "instruments."
Some VST's are freeware, and some are for pay. A few are heavy-duty $'s. You will see them included with many audio-editing and music-making programs. PrE can work with some. PrPro with some too. Audition can work with many more. Programs, like ProTools can work with even more.
Hope that helps,