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Apr 1985

Volume 77, Issue S1, pp. S1-S108

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back to top Session U. Musical Acoustics II: Modal and Finite Element Analysis Applied to Musical Instruments
Invited Papers
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The influence of the musician on the vibrational behavior of a violin (A)

Kenneth D. Marshall

J. Acoust. Soc. Am. Volume 77, Issue S1, pp. S44-S45 (1985); (2 pages)

Online Publication Date: 12 Aug 2005

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Modal analysis techniques were used to take a “first look” at how the presence of the musician alters the vibrational behavior of a violin. Animated mode shapes of a freely suspended violin will be presented, and compared to the response of the same instrument when held by five different players. The results show that the player imposes a constraint, or boundary condition, to the neck and lower bout of the violin, consisting primarily of a strong viscous damper acting in parallel with a weak spring. The resonant frequencies and mode shapes are only slightly affected, but the amplitude of the response of the violin is significantly lowered. It is concluded: (a) A variety of different violins should be measured for comparison purposes and to establish a decent data base. (b) A violin should always be measured freely suspended. Boundary conditions can always be added later in a mathematical model, but it is extremely difficult to remove a constraint that is present in the test data.
FREE

A finite‐element model of the guitar top plate (A)

B. E. Richardson and G. W. Roberts

J. Acoust. Soc. Am. Volume 77, Issue S1, pp. S45-S45 (1985); (1 page)

Online Publication Date: 12 Aug 2005

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Finite‐element analysis provides a viable, if inelegant, method for predicting the normal modes of vibration of strutted anisotropic plates for a variety of boundary conditions. The paper will discuss the problems and successes we have encountered in the formulation of a finite‐element model of the guitar top plate. It will deal with the choice of package and elements for the particular problem and will discuss one solution to the problem of modeling asymmetrically mounted anisotropic struts. The paper will conclude by reporting on the current status of the model and out attempts to predict the sound radiation from the plate in response to a typical string force acting at the bridge.
Contributed Papers
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Modal analysis of classical and folk guitars (A)

John Popp, Uwe Hansen, Thomas D. Rossing, and William Y. Strong

J. Acoust. Soc. Am. Volume 77, Issue S1, pp. S45-S45 (1985); (1 page)

Online Publication Date: 12 Aug 2005

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The mechanical responses of three freely supported guitars have been studied both under impulsive excitation and under excitation with a sinusoidal force [J. Popp and T. D. Rossing, J. Acoust. Soc. Am. Suppl. 1 76, S26 (1984)]. The normal modes of vibration as determined by the two different methods have been compared, and the agreement is found to be quite good. A comparison is made with the modes of vibration recorded in one of the guitars with the ribs fixed using time‐average holographic interferometry.
FREE

Vibration and decay characteristics of electrical basses (A)

Gordon Ebbitt and Hideo Suzuki

J. Acoust. Soc. Am. Volume 77, Issue S1, pp. S45-S45 (1985); (1 page)

Online Publication Date: 12 Aug 2005

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One of the assets of electric musical instruments such as guitars and basses is that they posess very long sustain. Since no acoustic radiation is required from the body of the instrument, very rigid and massive elements may be used in its construction. This will generally ensure that the sustain is long and constant from note to note. Structural resonances, however, occur in all structures with finite stiffnesses and masses and these resonances will influence the sustain of the instrument. Since the resonances occur at discrete frequencies, certain notes may have a more rapid decay than others and this may cause “dead spots” at certain notes. The relation among the structural resonances, the decay rates, and the input inertances at the ends of the speaking lengths of the strings of an electric bass will be discussed. The modal shapes will be shown and their shapes relative to the speaking length of the string will also be considered.
FREE

Effects of damping violin interior air modes (A)

Carleen M. Hutchins

J. Acoust. Soc. Am. Volume 77, Issue S1, pp. S45-S45 (1985); (1 page)

Online Publication Date: 12 Aug 2005

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The effects of having 65 holes, each 6 mm in diameter, in the ribs of a violin so that they can be left open or plugged with small corks have been discussed and demonstrated. Critical comments suggest that the marked reduction in tonal output when the violin is played with all holes open could be due to the quadrupole effect. To check this, E.A.G. Shaw has provided acoustically tailored tiny soft foam cylinders to plug the holes which are calculated to absorb the interior air modes. The effect of all holes plugged with corks, all holes open, and all holes plugged with soft foam will be discussed and demonstrated.
FREE

A finite element analysis of the violin body (A)

George Knott

J. Acoust. Soc. Am. Volume 77, Issue S1, pp. S45-S45 (1985); (1 page)

Online Publication Date: 12 Aug 2005

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The normal modes of a violin body were studied using finite element methods. The NASTRAN finite‐element analysis package and PATRAN‐G pre/post‐processor graphics software were the workhorses for this “computer laboratory” investigation. Free finite‐element top and back plates were first “tuned” to generally accepted parameters and were then assembled into a complete body consisting of the plates, bassbar, sound post, and end blocks. The normal modes of the finite‐element body compare favorably with those obtained from an impact hammer modal test on a real violin. Animated graphics of the normal modes, which provide significant insight into the physics of the violin structure, will be presented.
Invited Paper
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Discussion of modal and finite element analysis technologies applied to musical instruments (A)

Carleen M. Hutchins

J. Acoust. Soc. Am. Volume 77, Issue S1, pp. S45-S45 (1985); (1 page)

Online Publication Date: 12 Aug 2005

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Since research in this area is relatively recent, an informal discussion period is planned for those interested in exploring and sharing experiences in the progress, problems, and potentials of modal and finite‐element analysis applied to musical instruments.
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