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There is a tremendous amount of mystery that surrounds the instruments of Antonio Stradivari. There have been many studies done in the past, but no one completely understands exactly how he made his instruments, or why they are still considered the best in the world. This project is designed to develop an engineering model of one of Stradivari's vi...
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Citations
... More recently, Hutchins (1962) and Cremer (1984) have also provided overviews of the physics of the violin. Contemporary researchers have augmented these surveys with work on the influence of the violin varnish (Lämmlein et al., 2021;Skrodzka et al., 2013), the anisotropy of the wood (Stanciu et al., 2020) and has even enabled the investigation of high-end violins using CT-scans and performing reverse engineering (Pyrkosz, 2013). ...
... In order to understand all aspects of this complex instrument, we can try to deconstruct the violin and investigate the decoupled single parts, which was done by Pyrkosz (2013) and Tunlid and Värelä (2020). Once an instrument has been constructed, however, it is difficult (and irreversible) to disassemble it. ...
... CT has been utilized in investigating the violin [12] since the 1990s. In the 2000s, the CT method for studying violins was also used with a 3D model obtained by reverse engineering as a numerical analysis model [13]. Other nondestructive measurement techniques include optical 3D measurements, which are unsuitable for measuring the violin because they are sensitive to glossy surfaces and require the application of an antireflective, which reduces accuracy [14]. ...
... Further studies on the violin using modal analysis and the finite element method were pursued in [2][3][4] and more recent finite element simulations in [5][6][7][8]. In [9], the author takes a reverse engineering approach to investigate a Stradivari violin component-based and shed light on all components of the violin. The opposite way is shown in present research: the authors pursue a stepwise investigation of the violin. ...
Regarding structural dynamic behavior, the violin is a very versatile entity to study, since it combines many different effects in one single structure. Investigating this instrument means dealing with the uncertainty in natural materials, geometric nonlinearities, many interfaces, and sound radiation. Hence, this multifaceted structure serves as research subject for present work. The study starts with modal analyses of the raw spruce and maple woods, with the intention to show that an a priori material parameter identification is possible. The identified values serve as input for the orthotropic violin plates in the associated finite element model. Using 2D laser scanning vibrometry, the modal parameters are obtained for each plate. The components are supported on soft foams and on cotton wool in order to show the significant deviations in the measurement results with varying foam compliances.
... Many models of musical instruments have been developed for decades, especially violins since the 1980's [1]. More recently, models have been developed for the reverse engineering of a violin [2] or the study of dynamics and acoustics of violin body [3] and the way geometric properties interacts. Models have also been developed to screen material properties of the wooden constituents of the violin [4] and as a decision support tool for violins and guitars [5]. ...
... The vibrational behavior of violins has been widely studied and exhibits large variabilities in behavior [1]. Numerical models have been developed over the last decades, from [2] and [3] who used the nascent finite element method to more recent work with refined numerical models that exhibit behavior close to real instruments [4][5][6][7][8]. The objective of the present study is to investigate the effects of violin design and environmental conditions on its dynamical behavior and in particular on the bridge hill phenomenon [9]. ...
The behavior of stringed musical instruments have historically been investigated primarily through experimental studies and simplified analytical models. In this study, a physics-based model of a violin is used to determine the most influential design and environmental factors impacting its vibrational behavior. A global sensitivity analysis is performed based on the frequency responses of the violin and includes geometric and material properties as well as climatic conditions. In particular, this study attempts to provide a better physical understanding of the bridge hill effect.
Experiments are performed in a Mach 2 wind tunnel to investigate the vibration of a compliant panel under a ramp-induced shock wave/boundary layer interaction (SBLI). The panel is made from brass shim stock of length and width 122 mm × 63.5 mm. It is located just upstream of a 20° compression ramp that creates a shock-induced separated flow, where the mean separation length scale is about two boundary layer thicknesses. The region of the separation shock foot is characterized by large pressure fluctuations. These increase vibration amplitudes of the higher panel modes and especially the second mode, which has an antinode near the shock foot region. This work uses aeroelastic tailoring to reduce the panel vibration induced by the large pressure fluctuations of the shock foot. A thin rib is attached in the spanwise direction to the lee side of the panel at the location of the mean separation line of the SBLI. Stereoscopic digital image correlation is used to obtain time-resolved, full-field displacement fields during wind tunnel runs. Three different panel configurations are tested. First, a baseline case is established with a plain panel of thickness h = 0.254 mm. Then the rib is attached to the panel using double-sided, viscoelastic tape. Finally, the rib is attached directly to the panel using an epoxy adhesive. The results show that adding the rib in either configuration reduces the overall panel vibration by about 50% but especially reduces the vibration of the second mode. The configuration with the tape adds mass and damping to the system and is more effective at vibration reduction than the configuration with the epoxy, which increases mass and stiffness.
Timbilas are wooden xylophones finely manufactured and tuned by Chopi people from Mozambique. In the context of a research project concerned with historical Timbilas, we developed a workflow for the characterization and sound synthesis of Timbila bars using 3D scanning technology, reverse engineering and sound synthesis techniques. If the interest in 3D scanning is evident from the perspective of cultural heritage for documenting valuable objects without the need to make mechanical contact, the 3D data could also be used as inputs to computational methods for vibration and acoustic analysis. In this paper, we detail and apply the methodological framework to a real-life nine-bar Timbila, starting with the acquisition of the 3D data, moving to the finite element modeling and the modal computations, and ending with the building of a sound synthesis model based on physical modeling techniques. The proposed approach provides a non-invasive way of assessing the tuning of the bars and the reference pitch of the instrument, and also offers realistic synthetic sounds that can be exploited in combination with the produced high resolution rendering 3D model for applications in the fields of multimedia and virtual reality.
The use of internal cavity sound measurements to characterise the acoustic properties of any hollow-bodied string instrument is described using the violin family as an example. Measurements are described using inexpensive sub-miniature electret microphones as sensors for the impact hammer, both internal and radiated sound, and bridge admittance. The excited vibrations of the body shell are shown to excite a rich spectrum of internal cavity resonances, which are strongly correlated with the radiated sound, particularly in the signature and transitional frequency ranges below around 1.5 kHz for the violin. Examples of how such measurements can be used as a working tool in the luthier's workshop and for research on the acoustics of string instruments of any kind or size are illustrated by measurements on the violin, viola, cello, and double bass.
The classical guitar is a popular string instrument in which the sound results from a coupled mechanical process. The oscillation of the plucked strings is transferred through the bridge to the body, which acts as an amplifier to radiate the sound. In this contribution, a procedure to create a numerical finite element (FE) model of a classical guitar with the help of experimental data is presented. The geometry of the guitar is reverse-engineered from computed tomography scans to a very high level of detail, and care is taken in including all necessary physical influences. All of the five different types of wood used in the guitar are modeled with their corresponding orthotropic material characteristics, and the fluid-structure interaction between the guitar body and the enclosed air is taken into account by discretizing the air volume inside the guitar with FEs in addition to the discretization of the structural parts. Besides the numerical model, an experimental setup is proposed to identify the modal parameters of a guitar. The procedure concludes with determining reasonable material properties for the numerical model using experimental data. The quality of the resulting model is demonstrated by comparing the numerically calculated and experimentally identified modal parameters.
Because violins are traditionally hand-crafted using wood, each one is unique. This makes the design of repeatable experiments studying some aspects of its dynamic behavior unfeasible. To tackle this problem, an adjustable finite element (FE) model of a violin soundbox using the geometry and behavior of the “Titian” Stradivari was developed in this paper. The model is parametric, so its design and material properties can be varied for before/after comparisons in both the frequency and time domains. Systematic simulations revealed that f-holes set lower in the top, as seen in some Stradivari violins (e.g., Hellier, Cremonese), raise the frequency of the Hill (a feature in the bridge mobility); conversely, the higher set f-holes seen in some Guarneri violins (e.g., Principe Doria) reduces such frequency. This agrees with the widespread belief that the high-frequency response of Stradivari violins is stronger than Guarneri violins. Changes in the response of the system were quantified once each part of the design was added, calling attention to the influence of the blocks on the behavior of signature modes, especially in the frequency and shape of B+1. A text file of the FE model is available in supplemental materials; it runs in ANSYS (free version), for which guides are included.
