One of the most important of the early acoustical researchers in the CAS was John Schelleng. This retrospective issue on air and wood modes focuses on two articles by Mr. Schelleng, along with eleven other benchmark papers. We thank Carleen Hutchins for writing a short biography of John Schelleng, selecting the articles, and providing an introduction to the retrospective. A collection of articles such as this has many advantages for readers. Firstly, the work of selecting and organizing articles revolving around the central theme has been done by a highly respected authority on the subject. Secondly, these articles allow readers to follow the development of ideas over a period of many years. Finally, the collection presents a range of perspectives, from theoretical to highly practical. We thank Paul Ostergaard and Jay VandeKopple for scanning and digitally processing these articles.
In addition to our retrospective, we also look forward in time in this issue. George Bissinger gives an update on the VIOCADEAS project and Ephraim Segerman presents information about wood structure and function. We also include book reviews on varnish and violin making, a summary of activities of the New Violin Family Association, a description of workshops and titles of preliminary abstracts for talks planned for ISMA 2001, and other features. Thank you for subscribing, and, as always, we are open to your suggestions and comments.
Jeffrey S. Loen
3 - From the Contributing Editors
VIOCADEAS - The Violin Octet Revisited by George Bissinger
5 - Some Aspects of Wood Structure and Function by Ephraim Segerman
A scientific theory is an assumed picture of what is happening that can reasonably explain all of the relevant evidence. That evidence can be just simple observations of phenomena. Careful measurements under controlled conditions are good to make. They create more evidence challenges a theory to try to explain, and if it fails, the theory is discarded. Only a failure to adequately explain evidence can invalidate a theory, not (as some assume) a lack of supporting careful measurements.
A series of theories are presented here that offer explanations of observed phenomena in terms of the wood structure, either physical or chemical (including absorbed water). They include explanations of permanent and recoverable inelastic bending, sound absorption during playing-in and reduced sound absorption in stewed and aged wood.
10 - A Tribute to John Schelleng by Carleen Hutchins
13 - The Violin as a Circuit by John C. Schelleng
(reprinted by permission from The Journal of the Acoustical Society of America, Vol. 35, No. 3, p 326 - 338, March 1963)
The paper applies elementary circuit ideas to bowed-string instruemnts and their component parts. Parameters are defined and calculations based on simple circuit diagrams for the main resonance and the air resonance; curves describe their combined performance. The relative importance of circuit resistances - wood loss, radiation, and wall-surface loss - is discussed. Wall-surface loss is an important component of air decrement. No material improvement is to be expected from change in decrement or enclosure volume.
A theory for the wolfnote is given in terms of the beating of two equally forced oscillations, together with a criterion for its occurrence and a method for its elimination.
The paper analyzes principles of dimensional scaling between members of the violin family and shows why the cello and viola are more susceptible to wolftone than the violin.
A study of impedance requirements in wood shows that flexural similarity depends on the parameter c/p (compressional velocity over density); high values are in general favorable in the top plate. In the violin, cross-grain losses probably exceed those along the grain.
26 - On Polarity of Resonances by John C. Schelleng (as published in CAS Newsletter #10, November 1968)
30 - On Higher Air Modes in the Violin by Erik Jansson (as published in CAS Newsletter #19, May 1973)
34 - The Cavity (Air) Modes of the Violin by C.M. Hutchins (as published in CAS Journal Vol. 1, No. 5, May 1990)
36 - Project Tiny - An Overview by Mary Lee Esty and Carleen M. Hutchins (as published in CAS Newsletter #31, May 1979)
39 - Evidence for the Coupling between Plate and Enclosed Air Vibrations in Violins by G. Bissinger and C. M. Hutchins (as publshed in CAS Newsletter #39, May 1983)
A transducer on the bridge of violin SUS #180 was used to initiate instrument vibrations. The output of a small acoustic driver placed in the lower bout was used to initiate internal air oscillations. An accelerometer placed at various positions on the top plate and a small pickup microphone inserted inside the instrument were used to measure top plate and enclosed air vibrations, respectively. By tracking the various resonances using a combination of these test methods while alternating between air and CO2 inside the violin, we are able to show that some of the resonances heretofore labeled "air", "wood" and "top plate" are caused by complex couplings between the wood of the body and its inside air modes. The significance of possible "impure" character for an important resonance is discussed.44 - Further Evidence for the Coupling between Player and Enclosed Air Vibrations in String Instruments by G. Bissinger and C. M. Hutchins (as publshed in CAS Newsletter #40, Nov. 1983)
The interior air in four different string instruments (standard violin, long-pattern Stradivarius model violin, mezzo-violin and 16" viola) was interchanged with CO2 and CCl2F2 to examine the coupling of plate vibrations to interior gas oscillations by shifting the frequency of these oscillations. The lowest frequency air modes, A0, Al and A2, could be identified reliably by correlating the results for all interior gases. These gas oscillations also showed significant plate coupling as evidenced by accelerometer measurements at three points on the top plate.47 - Effects of an Air-Body Coupling on the Tone and Playing Qualities of Violins by Carleen M. Hutchins (as published in CAS Newsletter #44, Nov. 1985)
52 - Air-Plate -> Neck Fingerboard Coupling and the "Feel" of a Good Violin by G. Bissinger and C. M. Hutchins (as published in CAS Newsletter #44, Nov. 1985)
54 - Al Cavity-Mode-Enhanced Fundamental in Bowed Violin and Viola Sound by G. Bissinger and C. M. Hutchins (as published in CAS Journal Vol. 1, No. 2, Nov. 1988)
Fourier analyses were performed of bowed instrument sounds produced by two violins, a mezzo-violin and a viola both when the internal cavity was filled with air and with CCl2F2 which reduces the cavity mode frequencies. The results generally demonstrated significant strengthening of the fundamental of a bowed note, when it coincided with the pertinent A1 cavity mode frequency for both gases, irrespective of the presence or absence of strong corpus resonances.57 - Some of the Effects of Adjusting the AO and the BO Modes of a Violin to the Same Frequency by Carleen M. Hutchins (as published in CAS Journal Vol. 1, No. 5, May 1990)
59 - Acoustical Effects of ~Dressing Down" a Fingerboard and/or Thinning the Violin Neck by Carleen M. Hutchins (as published in CAS Journal Vol. 1, No. 5, May 1990)
60 - Tuning the BO Mode in Four New Violins by Carolyn Wilson Field (as published in CAS Journal Vol. 2, No. 7, May 1995)
63 - Varnished and Very Curous Secrets, Cremona 1747, edited by Vincenzo Gheroldi reviewed by George Stoppani
65 - The Art of Violin Making, by Chris Johnson and Roy Courtnall reviewed by Jeff Loen