I remember playing around with some wavelength nonsense or something (can't quite remember what I did, was following instructions on the internet once and never again) to try to reduce some crowd background noise and boost the voice of a speaker in a video edit and the end result was fine but there was definitely something about it that I as the editor of that video picked up (because I always think there's something wrong with literally everything that I do) but could not due to not being anything in the same universe as a sound engineer begin to identify what the perceived problem might be.

Which one did you end up picking? :D