We look forward to ISMA 2001 to be held in Italy. Be sure to read the announcement on page 20 for initial information. [On our Web site, see the section on Conferences.]
CAS and the Journal are designed to facilitate discussion among researchers and makers. This issue provides an opportunity to accomplish that objective. George Bissinger is starting a very important research project that can dramatically increase our detailed knowledge of violin construction and acoustics. But to succeed he needs suggestions for developing a standardized procedure to measure instrument qualities. Please be sure to read his descriptions on pages 21 and 44 and offer your suggestions. Timely responses are needed because the measurement techniques must be decided and frozen while the collection of the database proceeds.
I also call your attention to the "Letter to the Editor" in which John Solonika poses a number of quesitons from a maker's perspective hoping to interest researchers in finding answers. This is the kind of interaction that CAS is designed to facilitate, and I hope we will see more of it and good results.
As always, we appreciate your feedback about the Journal so that it can be improved and better meet the members' needs.
A. Thomas King
The bouncing bow as used in rapic spiccato and ricochet bowing has been studies. Dynamical tests were made by monitoring the motion of the bow stick and the bow force history when the bow was played by a mechanical device against a force transducer as a substitute to the string. Bows made of wood, fiber glass, and carbon fiber composites were studied and compared, as well as a bow which was modified from the normal (concave) shape into a straight stick.
9 - On the Kinematics of Spiccato and Ricochet Bowing by Knut Guettler and Anders Askenfelt
A skilled string performer is able to play a series of spiccato and ricochet notes - short notes played with a bouncing bow - with each onset showing little or no aperiodic motion before a regular slip-stick pattern (Helmholtz motion) is triggered. The motion of the bow stick can be decomposed into a translational component and a rotational component with the axis of rotation close to the finger grip at the frog. In spiccato, the bow describes two periods of rotational motion for each complete cycle of the translational motion (down-up bow), giving two notes. Simulations reveal that in a well-performed, crisp spiccato the bow gives nearly vertical impacts on the string, and that the first slip of each note takes place when the normal bow force is near its maximum.
In ricochet, the bow is thrown onto the string in order to create a series of short, crisp notes in one single bow stroke. The player terminates the ricochet stroke by damping the rotational component. This is done by loosening the bow grip and being compliant to the reaction forces acting back on the frog.
16 - Effect of The Bass Bar on the Free Violin Top Plate Studied by Finite Element Analysis by J. Bretos, C. Santamaria, and J. Alonso Moral
The top plate of a violin with its bass bar glued to the inside was modelled using finite element analysis. The analysis permitted study of the effect of the bar on the vibrational patterns and eigenfrequencies of the free top plate. The results are interpreted from the pertinent musical viewpoint and are satisfactorily checked with the experimental measurements reported by other authors.
21 - Toward a Normal-mode Understanding of the Violin by George Bissinger
We describe a recently initiated, comprehensive project to: a) characterize the mechanical properties of violins, b) create a large normal-mode-based mechanical and acoustical database of violins over a wide quality range, c) statistically correlate measured properties with concurrent qualitative judgements of each violin, and d) generate a comprehensive computer model particular to each violin capable of simulating the sound of each instrument.
23 - Stiffness Values of Spruce Determined by Ultrasonic Tests by Daniel W. Haines
Ultrasonic tests yield stiffness values for spruce that are about 15% higher than stiffness values obtained by other means. Comparable results are obtained for other softwoods.
24 - The Musical Acoustics Research Library by Gary P. Scavone
The Musical Acoustics Research Library (MARL) is a collection of independent archives or libraries assembled by distinguished groups or individuals in the field of musical acoustics research. MARL is directed by representatives of each member collection, in conjunction with the Center for Computer Research in Music and Acoustics (CCRMA) at Stanford University, which maintains the contents of each library. Currently, MARL is comprised of the Catgut Acoustical Society Library, the Arthur H. Benade Archive, the John Backus Archive, and the John W. Coltman Archive.
Various primers, varnish ingredients, and varnish recipes commonly used in violin making were examined to determine their tonal qualities. The carrier material was spruce cut into 200 strips, both along-grain and cross-grain strips. Measurements were made of the effect of various varnish coatings on two vibration characteristics of the strip - stiffness and damping. The strips were either 2 mm or 3 mm thick, corresponding to the thicknesses found in the violin top plates.
Measurements were made of the eigenfrequencies and damping values of each strip at each coating of primer or varnish. Results are presented as a pseudo velocity of sound (square root of the ratio of stiffness and the mass of the strip) and a loss factor.
Different varnishes and treatments had a substantial effect on stiffness and damping properties of the wood, especially cross-grain specimens. The loss factors n measured 9 years after treatign the strips ranged from 0.89 to 4.1 that of the untreated wood. The velocity of sound c varied from 0.92 to 1.27 of the untreated wood. These values take into account a correction that results from measurements of 20 untreated reference strips (also measured after 9 years).
Meauring Frequency Response Functions and doing modal analysis of a violin before and after varnishing show that the results obtained by the strip method seem to be transferable to the application of varnish to the violin. Accelerance levels of the varnished violin are changed (on average by -2.6 dB), eigenfrequencies are shifted (in a range of +-6%), loss factors change (as much as 75%), and mode shapes are clearly modified in the higher frequency range (1500 Hz).
44 - A Standardized Qualitative Violin Evaluation Procedure? by George Bissinger and Fritz Gearhart
We wish to produce a standardized, ~30 minute long, qualitative evaluation procedure as an essential part of a comprehensive normal mode measurement program on a large number of violins. The evaluation by the violinist should provide specific mechanical and acoustical information of each instrument as well as an overall quality rating for later statistical correlation with measured mechanical and acoustical properties. We present a broad outline of such a procedure here but wish to encourage discussion and comments from researchers, violinists, makers, psychoacoustics investigators, and others in the musical acoustics community with experience in such matters to help optimize it.