| 1. |
- Molin, Nils-Erik, et al.
(author)
-
Eigenmodes of av violin body
- 1990
-
In: Proceedings / Nordic Acoustical Meeting 90 - NAM 90. - Luleå : CENTEK. - 9186998390 ; , s. 421-428
-
Conference paper (peer-reviewed)
|
|
| 2. |
- Molin, Nils-Erik, et al.
(author)
-
Parameters of violin plates and their influence on the plate modes
- 1988
-
In: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 0001-4966 .- 1520-8524. ; 83:1, s. 281-291
-
Journal article (peer-reviewed)abstract
- Noncontact measuring methods and numerical calculations are used in a study of musical instruments. First, a simple method to determine the material parameters of a blank to a violin plate is presented. Eigenmodes of rectangular free-free violin wooden blanks are determined using optical nondestructive methods, Chladni patterns, or tapping. Assuming orthotropic material, the first three eigenmodes for such a blank are calculated using the finite element method (FEM). It is shown that the frequency of each eigenmode depends on separate elastic parameters. With this one variable dependence, it is a simple task to determine effective material parameters for quarter-cut standard wooden blanks when the frequencies and mass are known. Second, the violin maker's problem with the influence of material and geometrical parameters on the vibration modes is investigated. Numerical models and corresponding real violin plates are made from the spruce and the maple blanks. Good agreement between calculated and experimentally obtained plate modes is found. Calculations with a 10% variation in each parameter are thereafter used to give information about the influence of overall plate thickness variation, of local thickness variations, of changes in arch-height, and of material parameters. Third, boundary conditions for the plates when glued to the ribs are examined in a pilot experiment.
|
|
| 3. |
- Fällström, Karl-Evert, et al.
(author)
-
Transient bending waves in anisotropic plates studied by hologram interferometry
- 1989
-
In: Experimental mechanics. - 0014-4851 .- 1741-2765. ; 29:4, s. 409-413
-
Journal article (peer-reviewed)abstract
- Propagating bending waves are studied in plates made of glass-fiber reinforced polyester. The waves are generated by the impact of a ballistic pendulum. Hologram interferometry, with a double pulsed ruby laser as light source, is used to record the out of plane motion of the waves. The interferograms have an elliptic-like symmetry for an orthotropic plate, while the wave pattern for a symmetric angle-ply reinforced plate has a symmetry about the axes of reinforcements. Experimental data are compared on one hand to analytical results obtained by assuming that the orthotropic plate can be described as if isotropic along the main axes, and on the other hand to numerical results from calculations using the finite-element method. The effective Young's modulus raised to power 1/4 is shown to be an important parameter for the description of the dispersive wave pattern. A defect in the plate alters the wave pattern in the interferograms significantly. This may have technical use.
|
|
| 4. |
- Gren, Per, et al.
(author)
-
Laser vibrometry measurements of vibration and sound fields of a bowed violin
- 2006
-
In: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 17:4, s. 635-644
-
Journal article (peer-reviewed)abstract
- Laser vibrometry measurements on a bowed violin are performed. A rotating disc apparatus, acting as a violin bow, is developed. It produces a continuous, long, repeatable, multi-frequency sound from the instrument that imitates the real bow-string interaction for a 'very long bow'. What mainly differs is that the back and forward motion of the real bow is replaced by the rotating motion with constant velocity of the disc and constant bowing force (bowing pressure). This procedure is repeatable. It is long lasting and allows laser vibrometry techniques to be used, which measure forced vibrations by bowing at all excited frequencies simultaneously. A chain of interacting parts of the played violin is studied: the string, the bridge and the plates as well as the emitted sound field. A description of the mechanics and the sound production of the bowed violin is given, i.e. the production chain from the bowed string to the produced tone.
|
|
| 5. |
- Jansson, Erik V., et al.
(author)
-
On eigenmodes of the violin—Electronic holography and admittance measurements
- 1994
-
In: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 0001-4966 .- 1520-8524. ; 95:2, s. 1100-1105
-
Journal article (peer-reviewed)abstract
- The present experimental investigation, using recently assembled advanced electro-optical equipment for vibration analysis of three violins, was conducted to seek answers to three questions. A general or global question: Which parts of the violin body are vibrating the most? And two questions related to tonal quality: Are basic low-frequency vibration modes of a musically superior instrument different from those of an inferior violin? Can some special vibration properties be found to support the ``bridge hill?'' Optically obtained vibration modes were recorded as well as frequency responses in the form of admittance measurements. The investigation showed that the vibration modes found earlier are representative both for the inferior violin and the musically superior instruments, although discrepancies can be seen, both in eigenmode shapes and admittance responses. The experimental results are also in quite good agreement with published results of the modal analysis of a violin. Further, the experimental results indicate that the transversal vibrations are mainly within the plates, but at low frequencies, the vibrations of the edges and of the ribs can be large and in-plane as well as transversal. At higher frequencies, the transversal vibration amplitudes are small at the plate edges and larger inside. The top plate tends to have the largest amplitude of vibrations. In the 2.5-kHz range the violin with the most clear ``bridge hill'' tends to have the largest vibrations of the plates.
|
|
| 6. |
|
|
| 7. |
- Jansson, Erik V., et al.
(author)
-
Optical modal analysis compared to modal analysis with digital electronic equipment
- 1988
-
In: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 0001-4966 .- 1520-8524. ; 84:1, s. 136-
-
Journal article (peer-reviewed)abstract
- Hologram interferometry and speckle interferometry have introduced powerful tools for "optical modal analysis." The vibration amplitudes at a single frequency are recorded simultaneously for all points of a surface. The excitation position and frequency are adjusted to give a normal mode by watching the vibration patterns in real time. In the common modal analysis with digital electronic equipment, the vibrations of a single point as a function of time are recorded for all frequencies simultaneously via the impulse response. Impulse responses for a large number of points are measured, analyzed, and recalculated to extract the normal modes. Investigations of two modes of a complicated object (a violin) using both methods showed differences. The position of the dominating antinodes agreed, but the distribution of the vibration amplitudes and especially the nodal lines did not always agree. The differences seem to depend mainly on methods. The differences imply that great cautiousness is motivated in interpreting unknown vibration modes of objects with complicated structures and boundaries. The real time observation with the optical modal analysis offers hereby advantages
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
- Molin, Nils-Erik, et al.
(author)
-
Transient wave response of the violin body
- 1990
-
In: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 0001-4966 .- 1520-8524. ; 88:5, s. 2479-2481
-
Journal article (peer-reviewed)abstract
- In this investigation, the dispersive, transient wave propagation field of a complete violin excited by a mechanically induced impulse at the top of the bridge is presented. By means of double pulsed holographic interferometry with a ruby laser as light source the propagating wave field is recorded. From presented interferograms, it is seen that initially the top plate acts mainly as a nonsymmetric dipole with centers at the two bridge feet. The back plate is strongly coupled to the motion of the top plate by the sound post and acts more like a monopole. Thus the position of the sound post is crucial to the performance of the instrument. The free edges at the f-holes are very early reached by the dispersive bending waves of high amplitude probably giving a significant contribution to the sound of the violin family instruments
|
|
