Page 42 - Fall 2005

Whatʼs new in string instruments?
Thomas D. Rossing
At the ASA meeting in Vancouver we had a special session on Design and Construction of String Instruments followed by a workshop on this same subject. The workshop leaders were experienced builders of string instruments, and they shared their insights and some of their “trade secrets.” What follows are some excerpts from their presentations. At some later time, it might be possible to publish the complete texts.
Violins: Joseph Curtin, Ann Arbor, MI
The violin was perfected in 18th century Italy – or so tra- ditional wisdom would have us believe. But for all its beauty, the instrument is rife with unresolved design issues: It is easi- ly damaged, musically unstable, uncomfortable to play, tricky to adjust, and it must be played for decades or even centuries to sound its best. Today a growing number of makers are try- ing new approaches to their craft. As one of them, I believe there are at least seven directions in which the instrument can evolve:
Increased durability—To put an instrument in a musician’s hands is to put it in harm’s way. Most of the damage is entire- ly predictable and preventable with fairly modest changes to the violin’s design and construction.
Stability with changing humidity—Wood is hygroscopic. Changes in moisture content throw violins out of adjustment and can cause the wood to crack. Traditional varnish does lit- tle to impede vapor transfer. It is not hard to imagine alterna- tive finishes that do a far better job, and there are a variety of wood treatment processes that promise decreased sensitivity to moisture. Alternatively, non-hygroscopic materials such as graphite fiber can be used.
Ergonomic—The shape of violin-family instruments, while pleasingly symmetrical, makes it difficult for players to access the high positions, especially in the case of the viola, cello, and double bass. There are many ways to sidestep this and other ergonomic problems. Innovative designs will make instru- ments that are less taxing to play, thus reducing the risk of ten- donitis and carpel tunnel syndrome.
Adjustable by the player—Virtually all adjustments other than tuning the strings must be performed by a professional violin- maker, who must try to interpret the player’s often highly sub- jective requests. Makers are currently experimenting with con- figurations that allow the player to quickly and safely adjust the neck angle, the sound post length, the tuning of the bridge, the tension of the bass bar – and even the frequency of the lowest air resonance.
Ultra-light construction—The best old violins tend to be rela- tively light in weight, and this contributes to their power and responsiveness. Alternative materials such as graphite, balsa, and synthetic foam (along with innovative ways of using tradi- tional materials) allow the construction of vastly lighter instru- ments. I believe that within a decade these will radically rede- fine our concept of the violin.
High quality when new—There are well-documented acousti- cal differences between old Italian violins and our own – most
significantly the ability of the old ones to suppress the high- frequency overtones that can make new instruments sound harsh. An old Italian top, when taken off the instrument and tapped, sounds more highly damped than a new one. I believe this is mainly a question of what happens to wood over time. Once this is better understood, makers will either find ways to modify new wood or else develop combinations of other mate- rials that give the required acoustical behavior.
Twenty-first Century aesthetics—Classical violinmaking ended in the late 1700s, but no one knew what to do next so the same thing was tried over and over. Old Italian violins are clas- sics because they could not have been built in any other time than their own. Today’s violins will become classics only if they reflect the aesthetic and design ideals of our own time. It is happening already. I cannot imagine a more exciting time to be a violinmaker!
The Violin Octet: George Bissinger, East Carolina University
The Schelleng 1963 scaling, employing a two-mode basis set (main air = A0 and main wood = B1) was partially suc- cessful since the flat plate scaling for the top and back plates generally placed the B1 where desired, even though there were substantial variations in instrument shape. The real failing came in the Rayleigh relationship scaling for A0. This came about because A1 was never included in the octet scaling but was seen to be coupled to A0 as can be seen directly in the Shaw model of 1992, and this affected its volume dependence strongly.
An important improvement in scaling would be to go to a four-mode basis set: A0 and A1 for the cavity modes using Shaw’s two-degrees-of-freedom model with a semi-empirical wall compliance correction, and B1- and B1+ using flat plate scaling plus empirical relationships between top and back mode frequencies and assembled instrument B1 modes.
Classical Guitar Construction: Bernard E. Richardson, Cardiff University
As an acoustician passionately interested in the making of classical guitars, it is all too easy to get wrapped up in modes of vibration of the body and the effects that changes to shape and materials have on these modes. The complete chain of music making on the guitar, of course, involves the player and his or her interaction with the string, the string vibrations and their coupling to the body, and finally the coupling of the body with the surrounding air. We might importantly add the ear and brain of the listener, too, for without the due regard to the subjective evaluation of a listener, much of our acoustical endeavors would be wasted. Our recent guitar studies have involved an amalgamation of real measurements of both struc- tural vibrations and their associated sound fields (see Fig. 1) and modeling of a plucked string coupled to a radiating body. The model is used as the source of psychoacoustical evalua- tions of sound quality. Although it is tempting to ask questions
40 Acoustics Today, October 2005