Harvest (wine) of wine, winemakers would use the sugar and acid levels of the grape as a guide in determining ripeness. Early winemakers tasted the grapes to gauge ripeness. Modern winemakers use a refractometer to measure high sugar levels and °Brix or titration tests (using an indicator such as phenolphthalein) to determine the titratable acidity within the grape. In recent times there has been more of an emphasis on the "physiological" ripeness of the grape, usually in the form of tannins and other phenolics. Currently, tasting is the only way to measure tannin ripeness, which can take experience and skill to do
High frequency content measure useful for some applications, such as onset detection. The measure has close similarities to the spectral centroid measure, being essentially the same calculation but without normalization according to overall magnitude. High frequency content measure In signal processing, the high frequency content measure is a simple measure, taken across a signal spectrum (usually a STFT spectrum), that can be used to characterize the amount of high-frequency content in the signal. The magnitudes of the spectral bins are added together, but multiplying each magnitude by the bin "position" (proportional to the frequency). Thus if "X"("k") is a discrete spectrum with "N" unique