(modified 7/2016)
... I want to mention a summary of the recent tap tone research, so far (2016). This information might prove useful in isolating acoustical problems or in selecting a violin for yourself.
In its simpilist form, the tap tones of these areas should be in their correct relationshipa in order for the best acoustical playing condition.
...The (underside tap of the) neck the fingerboard/ nut / saddle and string bar of the tail piece, top plate, bass bar, and sound holes should match and be a 176 HZ. {Approximately 'F' below middle 'C' on the piano.}
The bridge, tailpiece proper, ribs, side tap to the neck, sound post, the scroll shape all around its curves, end pin, and back plate should match and be at 198 HZ {'G' below middle 'C' on the piano}.
...Tapping with the eraser end of an ordinary wooden pencil (or similar tap tool) should give good results on varnished areas, and tapping with a 6" piece of viola sound post stock should give good results the rest of the wood areas that need to be tested/recorded.
Next, current research shows that the frequencies of these parts should be at certain ideal frequencies. These then order the set of tuned frequencies for each individual part so that the violin works in unison acoustically. These frequency pairings (based on combination of Solfeeggio and C.37.C theory) are as follows:
C.37.C (HZ).......Solffeggio (HZ).........
142.5..................142.5..........
150.0..................148.5........... Note: no space for the text!
161.0..................160.0.....
177.0..................176.0.... Top plate, string bar of tail piece, nut, saddle, bass bar, neck, fingerboard, and sound holes.
188.0..................185.3..... Note: no space for the text!
...Now what about plate graduation before acoustical tuning?
... I would suggest this practical guide;
...For the top plate, make the plate 2.6mm even all over (except ends and edges).
...For the back plate, use my latest Guarnarie back plate graduation plan.
...I suspect the results will reward your efforts!
(c) 2016 by David Langsather