Remember to forget me!
Steve, did you see Esox's trademarked green squiggle line affair a few pages back? The concept there was that the blade is loaded towards the cap, but so heavily that it effectively pivots around the lip of the cap, taking pressure off the back edge of the support face. I wouldn't say that was likely on the Jagger, but I haven't seen enough other razors first hand to say that it might not be a potential culprit on some razors.Don't think of it as physically coming off the cap. Rather as a wave going through the blade, maybe causing increased & decreased pressure, maybe causing almost microscopic localized separations. Either way, I'd think it would act as if it wasn't rigid. And either way should be enough to produce sound. Maybe there wouldn't be any sound at all at 20N, at least none caused by that part of the blade, corresponding to a highly rigid state. And maybe even at 1N the sound only ever comes from the part that sticks out, but I doubt that.
High speed cameras? Fourier transform of the sound? A fourier transform converts from amplitude to frequency, so we can see the set of frequencies at each point in time. From there we might be able to figure out which piece of metal is vibrating. There's software that can do the transform on a WAV file.