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Journal of the Acoustical Society of America

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Apr 1991

Volume 89, Issue 4B, pp. 1851-2015

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back to top Session 5MU: Musical Acoustics: Bowed Strings: Honoring Carleen Hutchins, Part 2
Invited Papers
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Acoustics of the violin as a function of its parts (A)

Erik V. Jansson

J. Acoust. Soc. Am. Volume 89, Issue 4B, pp. 1926-1926 (1991); (1 page)

Online Publication Date: 14 Aug 2005

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During the last 20 years, Carleen Hutchins has successfully developed methods for testing and tuning of free top and back plates with Chladni patterns. Her methods have been successfully used by other makers in Sweden too. For the engineer/physicist, it is, however, difficult to understand how and how much of the quality of a violin is predicted by the free‐plate tuning. Therefore, data from KTH experiments have been used to investigate relations between free plates and assembled violins. Eigenmodes of free top and back plates have been calculated and measured. Effects of thinning the top plate free and in an assembled violin have also been investigated. Comparison of the frequency of the main resonance of the violin (T1 at about 500 Hz with mainly the top plate vibrating along the bass bar side) is affected somewhat similarly to thinnings of the ring mode of the free plate (i.e., it is most sensitive to off‐center thinnings and it should be a balance in stiffness along and across). Thus the present result is qualitatively in agreement with that of Dr. Hutchins—the ring mode of the free plate is the most important for tuning. Recent playing tests imply, however, that the lengthwise stiffness of the top plate is more important than the one across. [Work together with Luleå Technical University, L. Frydén, Stockholm, L and B. Niewczyk, Poznan.]
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The influence of the bow on aperiodicity of violin notes (A)

Robert T. Schumacher

J. Acoust. Soc. Am. Volume 89, Issue 4B, pp. 1926-1926 (1991); (1 page)

Online Publication Date: 14 Aug 2005

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A method has been demonstrated to investigate the aperiodicity in nearly periodic signals [R. T. Schumacher and C. Chafe, ICASSP‐90, Paper 6.A1.18, Albuquerque, NM (1990)]. This method, the norm difference method, quantifies the fluctuations in the shapes of waveforms from cycle to cycle. The norm difference method will be explained. As an application, a study of the difference in aperiodicity of a note separately played on a violin by two bows will be presented. In addition, a brief survey of the range of aperiodicities exhibited by other orchestral instruments will be presented in order to compare them with characteristic bowed string aperiodicities.
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The dynamics of musical strings (A)

Maurice Hancock

J. Acoust. Soc. Am. Volume 89, Issue 4B, pp. 1926-1926 (1991); (1 page)

Online Publication Date: 14 Aug 2005

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The resonance contours of a number of musical strings have been traced when operating in isolation from an instrument body, with more precisely defined loading and terminal conditions than are found in normal use, and with very small excitation amplitudes. For plain steel piano strings, results from the fundamental to the 25th overtone are broadly in accordance with the predictions of the standard classical theory for a lossy stiff string, but close agreement with calculated data cannot be obtained for any one set of the relevant parameters, and some disturbing influences are clearly in operation. Some of the resonances show double peaks suggestive of close coupling between slightly dissimilar modes, and for these and the single peaks, associated transverse resonances perpendicular to the line of the driving force are often found. A copper wire string hammered to produce an exaggerated linear distribution of deformation shows a more pronounced pattern of double and transverse resonances, and it is surmised that these occurrences with the steel strings are due to small departures from exact cylindrical uniformity. Overwound strings show similar anomalies with significantly higher losses.
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Acoustical significance of the violin octet (A)

Carleen M. Hutchins

J. Acoust. Soc. Am. Volume 89, Issue 4B, pp. 1927-1927 (1991); (1 page)

Online Publication Date: 14 Aug 2005

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The 30‐year acoustical and musical development of the violin octet has shown the following. (1) New instruments of the violin family can be created with fine tone and playing qualitites based on acoustical parameters, free‐plate tuning, and skilled violin making. (2) The prime controlling factor differentiating overall tone quality of the violin from that of viola, cello, and string bass is frequency placement in relation to string tuning of the body length air cavity mode (A1) originally called the “main wood” resonance. (3) The secondary controlling factor for tone quality, especially on the two lower strings is frequency placement in relation to string tuning of the A0 cavity mode originally labeled “Helmholtz” or “main air” resonance. (4) For instruments smaller than the cello, the A0 cavity mode frequency is controlled more by air volume than by compliance of the top, back, and ribs (sides). (5) For cello and larger instruments the A0 cavity mode frequency is controlled more by compliance of the top, back, and ribs than by air volume. (6) Due to greatly increased compliance of the wooden walls of basses, it has been found structurally unsafe to make ribs shallow enough to place the A0 cavity mode seven semitones above the lowest note as our scaling theory projected originally. These findings will be discussed and illustrated.
Contributed Papers
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Dynamic mechanical properties of violin wood (A)

Edwin R. Fitzgerald

J. Acoust. Soc. Am. Volume 89, Issue 4B, pp. 1927-1927 (1991); (1 page)

Online Publication Date: 14 Aug 2005

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Values of complex shear compliance (J∗ = J′ − iJ″) and modulus (G∗ = 1/J∗) have been measured for spruce and maple over a continuous frequency range from 2–10 000 Hz, and at temperatures from 15 to 40 °C. The wood strip samples of European spruce and Norway maple were supplied by Carleen M. Hutchins in connection with her investigations of the effect of various acoustical parameters of wood on plate tuning and the tone qualities of finished violins. Measurements were made in an automated electromagnetic transducer apparatus [E. R. Fitzgerald and R. E. Fitzgerald, Polymer Bull. 18, 167–174 (1987)] in which samples are sheared while clamped between stainless steel blocks. Values of the shear parameters vary with frequency, but also with the grain orientation, moisture content, and the perpendicular, clamping force on the sample faces while they are vibrated in shear. The mechanical spectra differ, but, in general, several sharp, microstructural compliance modes are superimposed on broad retardation, background spectra [E. R. Fitzgerald, J. Acoust. Soc. Am. 33, 1305–1314 (1961)]. Typical are the results for a spruce sample at 22 °C, sheared cross grain, for which values of elastic compliance (J∗) decrease from 2.74 to 0.306×10 9 cm2/dyn (2.74 to 0.306×10−2 MPa−1) as the frequency increases from 10 to 10 000 Hz; the loss compliance (J″) rises to a broad maximum of 1.65×10−9 cm2/dyn (1.65×10−2 MPa−1) at 4000 Hz. Values of the shear sound velocity and attenuation, together with the mechanical loss tangent (J′/J′ = G″/G′), are also calculated for the samples.
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Quasiperiodicity and bifurcations in wolf tones (A)

René Caussé, Jean Puaud, and Vincent Gibiat

J. Acoust. Soc. Am. Volume 89, Issue 4B, pp. 1927-1927 (1991); (1 page)

Online Publication Date: 14 Aug 2005

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The wolf tone, often obtained on the lower bowed stringed instrument, is studied with an experimental setup that mimics the true instrument with the help of a digital bow [Caussé and Weinreich, Proceed. 13th ICA, Belgrade 1989]. In this experiment, the resonant frequency of the bridge can be adjusted so that it is low enough for a good coupling with the fundamental frequency of the string, while keeping the bridge as rigid as possible. With this experimental setup, verification of the well‐known result that the wolf tone depends strongly on the pressure and speed of the bow and on the bowing point of the string has been made. By changing bow speed and pressure, by bifurcations after the normal periodic sound (Helmholtz motion), various quasiperiodic tones built on two or three basic frequencies have easily been obtained. Other possible scenarios related to bifurcation theory are indicated by observations of more complex signals.
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