Thanks for the return to sanity. Yes, as far as I can tell that's what I'm doing. Select a short speechless segment, sample that using "Get Noise Profile", then reopen the Noise Removal dialog with the whole file selected and click OK. I've tried a range of settings within the dialog, from both extremes to intermediate values, and no matter what, it doesn't leave the voice alone. I don't know how noise removal usually works, but I suspect it's by identifying frequencies in the sample and either eliminating or reducing those frequencies. So for a North American 60-cycle hum, or a British 50-cyle hum, it's a very specific target and easy to isolate. But here, the buzz is overwhelmingly load, and spans what looks to my untutored eye to be the same spectrum as the voice component. I've attached an image of the spectra so you can see what I mean.
If this is not how noise reduction works - I know it's a simplistic view, but I think it's close to the truth - then there may be tools to erase a repetitive spike such as we have here. If you have Audiocity yourself, and ten minutes to spare, please grab the samples I posted previously and give it a try. I've managed to salvage a number of the interviews with my own technique, but there are around 40 in total, all of 30 - 40 minutes, and some of them are hell to listen to, never mind correct.