In my last letter I noted that a CD of the Violin Octet in performance might soon be available. I am happy to tell you that the CD is now ready. You can find the details in the new Journal Department, Octet News, starting on page 47. I encourage everyone to purchase the CD. The players are excellent, and the performances show-off the instruments. Those who have never heard the Octet before will understand why Carleen and many others have been so enthusiastic.
I am very pleased to announce that Gregg Alf has agreed to serve as an Associate Editor for the Journal. Gregg brings enthusiasm and an interest in making the Journal relevant to practicing luthiers. He and I would both like to receive your papers oriented to the application of acoustical research to violinmaking and to hear your suggestions for topics and treatments. Gregg replaces John Randerson, who resigned in order to give more time to the task of completing a book on violinmaking with Karl Roy. I greatly appreciate John's help over the past several years and will miss his continuing close involvement. The prospect of the new book is, however, a substantial compensation! John will remain a member of the Editorial Advisory Board.
As always, we appreciate your feedback about the Journal so that it can be improved and better meet the members' needs.
A. Thomas King
Using electronic TV holography, we have studied the vibrational motion of two violins, one a Hutchins violin previously studied by other investigators. We compare the vibrational motion of the violin when it is excited by a force applied to the bridge, an oscillating sound pressure applied internally, and the sound field from a loudspeaker. We compare the modes observed when the violin is supported at the neck and end button with those observed when it is supported on rubber bands, although the latter makes holographic observation of the modes more difficult. Lastly, we make some recommendations for clarifying the mode designations.
10 - Acoustic Properties of Some Australian and Indonesian Woods by Redes D. Harjono and John I. Dunlop
Measurements have been made of the acoustic properties of a range of Australian and Indonesian woods that may be of interest to musical instrument makers. A vibrating cantilever method was used to measure moduli and damping loss, in both longitudinal and transverse directions, of wood strip samples in the frequency range 50 Hz to 5 kHz. The results are related to the properties of woods used traditionally to make stringed instruments.
15 - The Influence of Different Machining Processes on the Acoustic Properties of Wooden Resonant Boards by Samo Sali and Janez Kopac
Three different machining processes (planing, sanding, and milling) were used to prepare square-shaped test specimens of spruce boards representing a typical portion of the guitar resonant board. The specimens were vibrated by impacting them with a small wooden ball. The resulting oscillations, measured by an accelerometer mounted on the board, were processed by a frequency analyser. The measured response of the differently machined boards was analysed statistically in terms of amplitude, damping and power spectrum, to distinguish the different acoustic properties of the boards. The study found that the type of machining had a strong effect on the vibrational, and thus acoustic, properties of the spruce boards tested.
22 - Emission Of Difference Tones From a Violin by Hajo G. Meyer and Hero P. Wit
Difference, or "Tartini," tones are heard when a double stop is played loudly on a good violin. Some have believed that the difference tone is purely a psychoacoutic effect generated in the ear. This paper shows that the difference tones are emitted from the violin itself, at a sound level some twenty to thirty dB below the level of the primaries.
24 - An Experiment in Wood Substitution on the Classical Guitar by Alan Carruth
For many years tropical hardwoods have been the mainstay of guitar builders. Many of these woods are becoming rare or endangered, and an active search for substitutes seems wise, but it is difficult to know in which direction to proceed. What wood properties are important to the final sound of the classical guitar, and would it be possible through changes in the design and construction of the guitar to compensate for the differences? To explore these questions two classical guitars were built of different woods, but with as many acoustical parameters as possible matched using free plate tuning and other methods.
Makers probably realize that normal mode analysis can offer great benefits in the interpretation of the mechanical vibrational characteristics of violins. It is less well known that the normal modes can be used to calculate radiation properties of the violin. These attributes, along with a quantitative measure of mode excitation at the bridge, are combined into a vibration-Radiation (V-R) model capable of predicting relative acoustic properties of the violin from its mechanical response alone. A visual analogue of the V-R model is introduced wherein makers "build" violin sound by choosing normal mode "blocks" with certain vibration-radiation attributes. The V-R model is then applied to exploring and interpreting acoustic changes produced by that quintessential mechanical modification of the violin, soundpost removal.
38 - A Measurable Effect of Long-term Playing on Violin Family Instruments by Carleen M. Hutchins
Tests made on violin family instruments over the years show that long-term playing increases the flexibility of the walls of the cavity so that an air-to-air test made inside the instrument cavity gives increased amplitude to many of the response peaks. The changes illustrated are of a viola played in a professional quartet for six years, a cello played by an aspiring soloist at the Curtis Institute for two years, and another played by an amateur intermittently for 3 years, along with a violin and a viola used for experiments and played very little.
41 - Nodal Line Seeker by Oliver E. Rodgers
A simple experimental device is described which can be used to determine roughly where the nodal lines of a violin are for the mechanical modes of vibration at which the instrument is radiating large amounts of sound energy. It has been used very constructively in experiments to investigate the detailed effects of sound post adjustments and corpus modifications.