CAS Journal
November 2001
Volume 4, No. 4 (Series II)

To Our Readers

In this issue we feature articles that should further our understanding and appreciation of bow/string interactions, the inner workings of the violin and the classical guitar, plate tuning, graduation systems, and tools for acoustical measurements. In addition we introduce some new features.

We begin with a description of an ambitious project to compile, map, and statistically analyze thickness graduation data. Next, we have an exceptionally clear and thoughtful discussion of the physical dynamics of bowing a violin string by Robert T. Schumacher. This subject is more complicated than it is often portrayed, and Schumacher helps to clear up some commonly held misconceptions about what happens when bow touches string. Instrument makers should take interest in a major new work that represents several years of research by Oliver Rodgers and Pamela Anderson. These authors have used finite element models to measure the effects of slight changes in arching height, wood thickness, bridge character, soundpost location, bassbar height, and other factors. Results show that modifying certain factors may have much more influence on tonal quality than others. For plate tuning enthusiasts, Robert Wilkins describes a method for using the shaker table to take plate tuning one step further. In addition, we are pleased to have the opportunity to publish a sampling of extended abstracts from the International Symposium on Musical Acoustics (ISMA), held in Perugia, Italy in Sept. 2001. These papers describe "cutting-edge" research on important subjects.

We introduce a new section entitled "Questions and Answers" to help provide feedback to reader's questions. This issue's question is concerned with finding specific sources for synthetic materials for musical instruments. In addition, we introduce features on interesting articles in other journals, and interesting internet pages. The internet has become a major resource for makers, researchers, and enthusiasts, and we thank Kelvin Scott for compiling some web links that may be of interest to our readers.

We are continually striving to improve the journal. Please send us your comments and suggestions.

Good reading!

Jeff Loen

Table of Contents with Abstracts


2 -


3 -

Letter to the Editor

4 - Comments on "Acoustic Radiation from Bowed Violins" by Oliver Rodgers


5 - Thickness Graduation Mapping: Methods and Goals by Jeffrey S. Loen

From the Editors

7 - Bowing with a Glass Bow: An Update by Robert T. Schumacher

Research Papers

13 - Finite Element Analysis of a Violin Corpus by Oliver E. Rodgers and Pamela Anderson

Part 1: A finite element calculation program is used to compute all mechanical vibrating configurations of a violin corpus up to a frequency of 2200 Hz (approximately one and one-half octaves above the open E string). Changes are then made to the violin and the effects on vibrating configurations and frequencies are calculated. Results suggest that top arching and top plate thickness in the vicinity of the f-holes are of primary importance in tone production. We also examine the role of wood stiffness across the grain with regard to frequencies in the nasal sound region just above 1000 Hz.

Part 2: Experiments conducted as a result of the Part 1 calculations confirm that
1. Few mechanical vibrating modes influence violin sound.
2. The f-hole region and details of bassbar design strongly influence tone.
3. Rib and top plate graduations in sensitive areas affect high frequency overtones and carrying power.

We stress the importance to violin makers of reopening an instrument to experiment with final plate thickness as a way of producing instruments with superior tonal characteristics.

27 - Violin Mode Relationships in Free Plates, after Attachment to the Ribs and in the Finished Instruments by Robert A. Wilkins

Vibrational modes of two violins are studied via matched free plates, with plates glued to the ribs, and finally in finished instruments. Mode changes and relationships are noted.

ISMA 2001 Extended Abstracts

33 - Admittance at the frets of a Classical Guitar by Ricardo R. Boullosa

Admittance measurements show that the energy input from the string towards the guitar body comes not only from the bridge in the soundboard, at some low-medium to high frequencies the energy comes also from the fretted end of the string. It is shown that the mechanical admittance is lower over a broad frequency range at frets located near the 'foot and heel' of the guitar, than that measured at other frets. The admittnace is relatively high at frets located over the body of the guitar, some comments on the influence of these results on the tone of the guitar is made. Some other measurements are reported with respect to the mode shapes of the lowest resonant frequencies of the neck.

37 - Vibrational Dynamics of the Resonance Box of a Guitar: Finite Element Method and Modal Analysis by M. J. Elejabarrieta, A. Ezcurra, C. Santamaria

A numerical model has been designed for a guitar resonance box implementing the Finite Element method. The vibrational behavior of the guitar box has been studied starting on its main components, assembling them and allowing the soundboard - back coupling via the inside air. The model allows one to study the influence of each component on the whole box, and the contribution of the modes of the components (wooden box and its parts, and air), to the coupled modes. The results of the numerical model have been compared with the experimental modal analysis of a real guitar box.

42 - Thickness Graduation Systems of Violin Family Instruments: Preliminary Statistics and Conclusions by Jeffrey S. Loen

Thickness data on 232 plates of violins, violas, and cellos constructed by 44 important makers have been systematically compiled using a geographic information system. Descriptive statistics, plus analysis of contour maps of plate thickness indicate that these instruments have highly variable graduations (often with extremely thin tops), and highly asymmetrical graduation patterns. These plates are quite unlike what is portrayed in modern violin making books.

Contour maps are used to define a membrane-like uniform system, a bull's-eye-like concentric system, and a backbone-like longitudinal system. Instruments made in Cremona, Italy from 1604 to 1745 by the Amatis, Guarnarius, Stradivari, and others display, with few exceptions, uniformly graduated tops and concentrically graduated backs. In contrast, the concentric system is used in both tops and backs made in Brescia, Italy prior to 1623 by da Salo, Maggini, and others.

45 - A Low-cost PC-based Tool for Violin Acoustics Measurements by Lars Henrik Morset

We present a PC-based technique for measuring important acoustical properties of the violin. The technique can be used with standard low-cost equipment to make a flexible tool for violinmakers. The problem of proper excitation by suitable transducers is discussed. We demonstrate how the tool can be used to estimate the radiation power and to detect the A1 mode of the violin.

49 -Impact of string stiffness on digital waveguide models of bowed strings by Stefania Serafin and Julius O. Smith, III

We propose a digital waveguide model of a bowed string instrument that accounts for string stiffness. We show how dispersion due to string stiffness can be accurately modeled and how it improves the quality of the synthesis.

Questions and Answer Forum

53 -

Book Review

54 - The Dance Master's Kit (La Pochette du Maitre a Danser) by Claude Lebet Reviewed by Jeff Loen

Interesting Information

55 - Articles in Other Journals

56 - Web Pages

Meetings Announcements

59 - International Musicological Society 17th International Congress (IMS 2002)

59 - International Symposium of Musical Acoustics (ISMA) Mexico City

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