I am thinking that any vibration of the steel is very small and likely not of major concern to the turner. To me the bigger problem is control of the "feed irregularities" which I suppose falls under the tool presentation category. In other words, it is a bigger matter to maintain consistent orientation of the cut with regard to rigidity in relation to the fulcrum. Of course sharp tools are a necessity, but I think are more important to the turner with regard to "feed irregularities" than any vibration that might be enhanced in the steel. Try turning a piece of Aluminum on the wood lathe and see how hard it is to keep the tool fixed so that it maintains consistency of the cut. Although a sharp tool improves your chances as does keeping the tool rest very close to the piece, you will most likely have some chatter marks because of your inability to keep the tool fixed with regard to its cutting orientation rather than because of any small amount of vibration that is occurring in a naturally flexing, but very ridged piece of HSS. I suppose really what I am saying is that I think the vibration within the tool steel that does occur is at a microscopic level and really not as big an issue as the macro level movement of the tool orientation that is inevitable in free hand turning provided you have employed other measures such as limiting tool rest distance in relation to the tool's girth/thickness. I think that any pattern forming on the wood is more likely a function of wood flexing and feed irregularities than tool steel vibration. That is why I wondered about the use of the term vibration because to me vibration is an oscillation from equilibrium about some mean value which I don't believe is necessarily what is happening with the tool orientation itself.