The "Modal Activity" is defined as follows: RMS Admittance Levels within a predefined frequency bandwidth (fu...fo) as function of the location on the violin corpus (Coord.)
1. Example: "Modal Activity" of two violins: Stradivari 1721 versus Stradivari 1712.
The red areas (0...12dB) represent areas with a higher vibration activity of the Stradivarius 1712, whereas the blue areas (0...-12dB) represent a higher activity of the Stradivari 1721. Only in the bandwidth 1200...2400 Hz the Stradivarius 1712 (top-plate) shows higher vibration levels as the other instrument. Especially in the first octave bandwidth 200...400 Hz the Stradivarius 1721 shows to be stronger. Indeed the late Stradivarius 1721 sounds darker and more voluminous than the earlier Stradivarius 1712 which has a somehow brighter sound:
2. The second example shows a comparison of "Modal Activity" between the violin of Antonio Stradivari 1721 (red) already mentioned above and a violin by Joseph Guarneri del Gesu 1733 (blue). It is obvious that the Stradivarius all in all shows higher vibration levels than the Guarneri del Gesu. The latter only shows clearly higher vibration levels in the upper top plate region:
3. Another example shows a comparison of "Modal Activity" between the Joseph Guarneri del Gesu 1733 (blue) already shown in the comparison above and a violin by Domenico Montagnana 1729 (red). It is obvious that these two violins show “softer” differences than the comparisons with the Stradivarius:
