Prof: interesting point about how a measurement (e.g., a 4 dB boost at 150 Hz) can express a "subjective impression" to another specialist who speaks the language of decibels and Herz. Of course, this presupposes that the subjective correlate ("warmer" male voice, or whatever) is causally connected to that measured phenomenon. I'm not saying it isn't, but I think a lot of folks on this site would want to say so, or would want at least to say that there are other, and important, subjective impressions that don't correspond to any known measurement. I'm not saying that isn't so, either; I really don't know. But your point about "objective" phenomena corresponding to subjective impressions in such a way that professionals who speak the technical language understand measurements in terms of their own subjective experience is revealing here.
By the way, Descartes was not a skeptic, despite the game he plays with his "method of systematic doubt" in, for instance, the first Meditation. On the contrary, Descartes deploys doubt not in order to show that everything can be doubted, but rather, to discover what can't be doubted, what therefore must be true. This skeptical starting point is motivated by historical circumstance: the intellectual dominance of Aristotle in medieval science, and the contamination (for lack of a better word) of philosophy by theology in medieval Scholasticism. Were it not for Descartes' clearing away everything doubtful and building his system back up from a foundation of certainty using only logic (or, at least in principle, only logic), "modern" science would never have been possible.