Judging a violin by tapping
Every now and then, lower-end instruments are being offered without strings/bridge installed. Then, one cannot judge the most important thing: the sound quality.
Would it be meaningful to test the sound of a violin just by tapping and listening to the sound, or maybe use software to obtain a frequency spectrum of the resonances? Probably, you'd need to install a bridge, held in place by at least one string (dampened by a rubber band), which can then be tapped on from the east/west-facing edges. If it isn't an original bridge, the feet wouldn't be cut to fit the belly surface. How bad would that be?
Supposing that it is possible to measure and judge the resonance spectrum, are there important acoustic properties of the violin that you would miss and that will only show when you actually play a fully set-up instrument?
Edit: never mind tapping a bare violin; just consider violins that are set up with bridge, soundpost, and strings.
I'm always worried about the subjectivity of my perception. I know from things like wine tasting, loudspeaker comparison, and even buying a new violin bow and trying out a friend's violin that I find it very hard to judge in absolute terms; I will mainly note differences (without good/bad label) when I switch and I get confused after a few tries.
Example case: I tried measuring tap spectra on my DIY travel violin (different thread). I was convinced that the bass response had increased after a move of the sound post. But the tap spectra were virtually the same.
Adding any bridge or strings without a soundpost is a bad idea and also will affect the sound. If they're being sold without a bridge or strings, the soundpost (if there is one??) will have likely fallen loose at some point and need to be reset before you can do much of anything with it.
I think that you will hardly see any concrete differences in the spectra of different violins with your method.
Both the above replies have made many excellent points, IMO.
It is impossible evaluating violins by tapping. Instruments with similar "tappings" will sound very different.
I think tapping is most useful when choosing a ripe watermelon :)
everytime i walk into a music store and see violins without bridges and strings, and i asked them about them, they always tell me the same answer "thats how they are stored" i always feel bad for the people that will buy them knowing the sound post probably moved and has bad strings that havent been used yet
I bet the store clerk did not know or care about the difference between a guitar and a violin in terms of maintenance requirement. I certainly was not aware there is such a thing called the sound post hidden inside the violin when I first bought the instrument. I also wondered why the bridge is not fixed (or glued) to the body.
Actually you can tell a clunker by tapping on it quite obviously, a violin that has good tap sounds usually sounds good when strung up, but not always, certainly better odds than random, tapping can be useful for violins that are not strung up, but its something of a skill to acquire from years of experience IMHO, not easy to teach someone.
I agree, also there are often peaks or holes in the spectrum that can tell a bit.
What you can tell is if the wood rings and is resonant, that's a good sign, if the tap tones sound like cardboard, dead as a door nail, there really no hope.
OK, those who mentioned that a bridge-less violin is likely to be soundpost-less as well: good point. I hadn't thought about that. So, I'll now just consider the usefulness of tapping the bridge of a violin that is set up.
obviously there's no better test than playing the instrument properly set up, no scientific testing is ever going to be a more accurate indicator of the tone than actually playing the violin, I was just speaking for the common case for me as a luthier of having the option to buy a violin that is not set up properly to play, at least for me tapping on violins can tell me which violins to avoid, and if the tap tones are good, more often than not, the tone is good as well.
Han N, I can understand your desire for an objective test, and fascination with a measurement approach. Evaluating violin tone with spectral analysis has looked so promising, that researchers have been aggressively chasing it for at least a couple of decades. However, it still has not managed to replace subjective impressions as the final arbiter, even for these researchers. (Martin Schleske is the only researcher I know of who may think it has.)
Doubtless there are violins around where only a cursory inspection is needed to determine that the tapping is best done with a 2 lb hammer to put the poor thing out of its misery ;)
Peter, the problem with in-store testing is that it may not be just a relatively empty room, perhaps like a recording studio, but a space in which the walls are adorned with perhaps dozens of violins and violas each of which is a resonator for the instrument under test. So what the tester is hearing is not just the sound of the test instrument but an overlay from all the surrounding resonances.
Trevor - the room in question was very small and long and it had highly reflective surfaces, walls, windows etc. The end result was that it made the instrument sound great because of all the reflections and at the same time muddied things up so the strings all sounded fairly equal. (Well known dealer in central London).
As a maker (and retired aerospace engineer), I have tried to use various means of judging instrument quality at all stages of construction, with the idea that I could make modifications at that point to improve things. It's pretty hopeless. At best, with a soundpost in place, you should be able to identify something truly horrid vs. something decent... with enough experience. Perhaps with a massive research program, you could get finer gradations of bad and good... but why? In the end, people often disagree on what's bad and good anyway, even with all the parts in place and able to be played.
At one point, a Strad was considered to be the sound to emulate. But with further experience and research, it was discovered that one Strad can sound radically different from another, and that in a lineup, a Strad isn't always the most preferred instrument by either the player or the listener.
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