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Microscopic structure of spruce and maple of common structure (RT radial-tangential plane, LT longitudinal—tangential plane, LR longitudinal—radial plane)
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The aim of this article is to correlate the experimental modal analysis (EMA) with finite element analysis (FEA) to study the effect of wood species on vibration modes of violin plates made of spruce and maple. For EMA, five violin plates each made of spruce and maple were tested (curly maple, quilted maple, common maple with regular and irregular...
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Metal lattice structures obtained through Selective Laser Melting may increase the strength-to-weight ratio of advanced 3D printed parts, as well as their damping properties. Recent experimental results showed that AlSi10Mg and AISI 316L lattices are characterized by higher Rayleigh damping coefficients with respect to the fully dense ma...
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). ...
... For violins, traditionally spruce is used for the top plate and curly maple is used for the back plate. The effect of wood anisotropy on the vibration modes of flat violin plates made of spruce and maple was demonstrated with FEA using three hypotheses: the material has the symmetry of an isotropic solid, a transverse isotropic solid or an orthotropic solid [171]. The hypothesis of this research was: the plates were edge-pinned, flat and of uniform thickness of 3 mm. ...
... Spruce plates, edge constrained-vibration patterns in three hypotheses of elastic symmetry. The displacement is indicated by the colour scale, ranging from blue (displacement zero) to red (maximum displacement, 1 mm)[171]. Maple plates, edge constrained-vibration patterns in three hypotheses of elastic symmetry[171].As regards the vibration of the spruce violin plate illustrated inTable 34, we note:-Wood anisotropy has no effect on the vibrations patterns for modes 1 to 6. ...
... The displacement is indicated by the colour scale, ranging from blue (displacement zero) to red (maximum displacement, 1 mm)[171]. Maple plates, edge constrained-vibration patterns in three hypotheses of elastic symmetry[171].As regards the vibration of the spruce violin plate illustrated inTable 34, we note:-Wood anisotropy has no effect on the vibrations patterns for modes 1 to 6. In thistable, only mode 6 is illustrated. ...
Acoustics is a field with significant application in wood science and technology for the classification and grading, through non-destructive tests, of a large variety of products from standing trees to building structural elements and musical instruments. In this review article the following aspects are treated: (1) The theoretical background related to acoustical characterization of wood as an orthotropic material. We refer to the wave propagation in anisotropic media, to the wood anatomic structure and propagation phenomena, to the velocity of ultrasonic waves and the elastic constants of an orthotropic solid. The acoustic methods for the determination of the elastic constants of wood range from the low frequency domain to the ultrasonic domain using direct contact techniques or ultrasonic spectroscopy. (2) The acoustic and ultrasonic methods for quality assessment of trees, logs, lumber and structural timber products. Scattering-based techniques and ultrasonic tomography are used for quality assessment of standing trees and green logs. The methods are based on scanning stress waves using dry-point-contact ultrasound or air-coupled ultrasound and are discussed for quality assessment of structural composite timber products and for delamination detection in wood-based composite boards. (3) The high-power ultrasound as a field with important potential for industrial applications such as wood drying and other applications. (4) The methods for the characterization of acoustical properties of the wood species used for musical instrument manufacturing, wood anisotropy, the quality of wood for musical instruments and the factors of influence related to the environmental conditions, the natural aging of wood and the effects of long-term loading by static or dynamic regimes on wood properties. Today, the acoustics of wood is a branch of wood science with huge applications in industry.
... For the complete characterization of musical instruments, we developed an integrated method [10], which combines ESPI [10,11], impulse response [10,11], FEM modeling and simulations [12][13][14][15][16][17][18], and sound perception. Here, we present the application of this integrated method and the corresponding results for the vibroacoustic evaluation of a novel carbon fiber bouzouki and its comparison to the characteristics of a classic wooden bouzouki. ...
An integrated method, which combines Electronic Speckle Pattern Interferometry, impulse response measurements, finite element method simulations, and psychoacoustic tests, is proposed to evaluate the vibroacoustic behavior of a carbon fiber bouzouki. Three of the carbon fiber instruments are manufactured, and one is qualified via interferometric experimental measurements with reference to a traditional wooden bouzouki, which was evaluated for its sound and playability by the proposed method. Psychoacoustic tests were used to evaluate the sound and playability of the newly qualified carbon fiber bouzouki, which was further modeled by the finite element method and simulated. The simulation results agreed well with the experimental measurements. Furthermore, finite element simulation results of the qualified carbon fiber bouzouki were demonstrated with reference to the traditional wooden bouzouki experimental results, providing new findings crucial for the optimization of the manufacturing and the vibroacoustic behavior of the carbon fiber instrument. The proposed integrated method can be applied to a variety of carbon fiber stringed musical instruments.
... The second approach, proposed by Alkadri et al., 2018 [14], is based on the measurement of wavelength, amplitude and grain angle measured in the transition point between peak and valley of the wave. In a previous article, [15], the angle of the fiber was measured according to the method proposed by Alkadri et al., 2018 [14], and an inverse proportional relationship between the wavelength and the curly grain angle was found. Starting from this conclusion, in the present paper we considered that the wavelength was sufficient to express the degree of undulation of the grain. ...
... The current question posed by musical instrument manufacturers is whether having the wavy grain in the wood contributes to the acoustic quality of the musical instruments or has only aesthetic value. In this sense, various studies have been carried out on the physical, mechanical and elastic properties of the wavy-grain sycamore maple wood, but none provided synoptic information regarding the relationship between the pattern of the wood and its elastic and acoustic characteristics [14][15][16][17][18]. ...
... These properties are correlated with the physical characteristics of the wood species. Studies on the elastic, acoustic and dynamic properties of resonance wood (spruce and maple) have been the focus of many researchers, providing a rich source of data [9,[11][12][13][14][15][16][17][18]. These studies investigated tone wood species from forest basins in Slovenia, the Czech Republic, Austria, Italy, France, Germany, USA. ...
The wood used in the construction of musical instruments is carefully selected, being the best quality wood from the point of view of the wood structure. However, depending on the anatomical characteristics of the wood, the resonance of wood is classified into quality classes. For example, sycamore maple wood with curly grains is appreciated by luthiers for its three-dimensional optical effect. This study highlights the statistical correlations between the physical and anatomical characteristics of sycamore maple wood and its acoustic and elastic properties, compared to the types of wood historically used in violins. The methods used were based on the determination of the acoustic properties with the ultrasound method, the color of the wood with the three coordinates in the CIELab system and the statistical processing of the data. The sycamore maple wood samples were divided into anatomical quality classes in accordance with the selection made by the luthiers. The results emphasized the multiple correlations between density, brightness, degree of red, width of annual rings, acoustic and elastic properties, depending on the quality classes. In conclusion, the work provides a valuable database regarding the physical–acoustic and elastic properties of sycamore maple wood.
... Long term drying is necessary taking about 10 years, for high quality of musical instruments. Therefore, kilndrying should be employed in the final stage of drying blanks, in order to reduce the wood moisture content of the raw material for violins to a final moisture content of (6-8)%, [11]. Two symmetric blanks side by side are glued along the maximum height in order to achieve a symmetric anatomic structure of violin plates (figure 1, c). ...
... The recording took place in the performance hall of the Brasov Philharmonic, Romania, under the same technical conditions. The evaluation of the acoustic quality of the tested violins was based on the completion of an opinion poll in which marks were given from 1 to 5, for five acoustic criteria relevant to artists: bright and strong tone; sound clarity; warm sound; amplitude of sounds and equal sound on all 4 strings, [11]. (https://docs.google.com/forms/d/e/1FAIpQLScyUUy ...
In this paper, the manufacturing technologies of violins, followed by a study on the psycho-acoustic evaluation of violins with different anatomic structure of wood are presented. The evaluation was performed by music experts (performers, teachers, students) based on music auditions of excerpts recorded on the violins studied. The musical performance was performed by the same violinist, under the same conditions. Respondents rated five acoustic criteria. The statistic results showed that age, experience, gender influence the acoustic perception and also that the geometric characteristics of the violins produce different acoustic impressions.
... Thus the air pressure in the box changes periodically, acting as a Helmholtz type resonator. Taking into account the contour conditions, the sound waves are reflected and radiated by the walls of the box in all directions, producing the composition of sound waves under a rich spectrum of harmonics [6][7][8][9][10]. Estimations of the elastic and acoustic properties were made by methods based on ultrasound [ 4,[10][11][12][13][14][15][16]. ...
The sound post is a very important element in the acoustics of musical instruments with strings and bows. This paper presents the experimental investigations regarding the elastic and acoustic properties of the wood used to obtain the sound post. The speed of propagation of sound waves in wood and then the determination of the elastic properties in the longitudinal direction was measured on a number of 12 sound posts made from new and old resonance wood. It was found that the elastic and acoustic properties depend on the degree of aging of the wood. Thus, the longitudinal propagation speed is about 4% higher in samples of freshly processed wood compared to those of aged wood; the longitudinal modulus of elasticity is about 19% lower for aged wood samples.
... After the loading period of the part with a certain load, the deformation -respectively the latent flow is characterized by three zones: the primary flow, the secondary flow and the tertiary flow. Experimental research has shown that wood and wood materials are highly sensitive to stress, temperature and humidity [4][5][6][7]. Dynamic methods for mechanical analysis (DMA) are used to determine the viscoelastic behaviour of wood. ...
... The principle of the method is to cyclically apply an oscillating force at different values of temperature and / or frequency of stress to the studied specimen. Based on the response of the specimen, the viscous behaviour of the material in the form of the loss modulus as well as the stiffness of the specimen in the form of the preservation modulus can be determined [3][4][5][6]. These properties are often described as the ability to lose energy in the form of heat (damping) and the ability to store energy to return to its original shape after deformation (elasticity). ...
The paper presents the experimental investigations regarding the viscoelastic behaviour of maple wood used in the construction of stringed musical instruments. The studied samples were classified according to the anatomical structure of the wood in the four classes of anatomical quality used by the manufacturers of musical instruments. Based on the mechanical analysis in dynamic regime, the viscoelastic parameters were determined - the preservation module E', the loss modulus E' and the damping tan δ, in conditions of constant temperature, respectively variable temperature. It was found that the determined rheological quantities depend on the anatomical structure of the wood, the frequency of the excitation and the temperature.
... These are related to the quality of the wooden material used to manufacture the instrument and its accessories, the quality of the other materials used in the construction of a violin (e.g., strings), the type of varnish (lacquer) and the varnishing technology used, the skills of the violin maker, the skills of the musician, etc. Any modification-e.g., using a different wood species than maple for the back plate [11,12], or changing the position of the sound post, or increasing the number of varnish layers, or changing the drying time after applying each varnish layer, or changing the thickness of the plates-may affect the sound quality [13][14][15][16]. Optimization is possible only by a combined assessment, which must take into account both an objective evaluation, based on the determination of some measurable parameters, and a psycho-acoustic evaluation, based on the perception by specialists in the field of music (soloists and listeners). ...
This paper presents the results of an experimental study performed on seven violins obtained from a top plate made of resonance spruce and a back plate made of curly maple. Each pair of plates had a different modification to its thickness profile. Some were thickened and others were thinned compared to the classical thickness profile. Then, a soloist played a musical sequence on each violin and the acoustic signals were recorded. The sound quality of the signals was evaluated with a psycho-acoustic evaluation based on a blind questionnaire completed by listeners. It turned out that: (1) respondents with more musical experience (especially those with over 26 years of experience) were more demanding in assessing sound clarity and offered the widest range of scores in assessing this quality; (2) the musical experience of the respondents influenced to the highest degree the appreciation of the warm sound quality; (3) the scores for the violins with thinned plates were weaker, especially according to the psycho-acoustic analysis; and (4) the highest score was obtained by the violin with the thickest plates, which can be correlated with the two dominant frequencies extracted from the FFT analysis, whose values coincide with the frequencies of the B1- and B1+ modes.
... Thus the air pressure in the thin walled structure changes periodically, acting as a Helmholtz type resonator. Taking into account the boundary conditions, the sound waves are reflected and radiated by the walls of the box in all directions, producing the composition of sound waves under a rich spectrum of harmonics [21,22]. The body of the violin converts the high vibration pressure from the string into the low pressure vibrations of the ambient air, thus achieving a phenomenon of ''impedance equalization''. ...
... In maple wood, these zones are less distinctive, and so in this case, it was more important to quantify the ''curliness degree'' of the grain. For this purpose, a quantitative method was developed [22,32,33], by using the same WinDENDRO Density imageanalysis system. The wavelength of the curly grain was measured in the tangential direction on the radial section of each sample (Fig. 3). ...
... growth rings i ≤ 0.5 mm. The maple violin plates for the back are very curly, having TRWi ≤ 1.3 mm and a wavelength of the curly grain of maple ≤ 3 mm[22,31,32]. ...
From a constructive and functional point of view, the violin body is a structure with thin walls having the role of amplifying the musical sounds and consists of an arched top and back plates, the ribs and the linings with thicknesses about 100 times smaller than the overall dimensions of violin body. The present research proposes to investigate: (i) the modification of the vibrational properties of the wooden arched thin plates in different stages of violin construction: as individual plates in preparation stages, then assembled in the violin body, after the addition of the neck and finally, as finished product; (ii) the influence of the plate thickness change on their vibrational behavior. The following dynamic properties were studied: frequencies of twisting mode #1, bending mode #2, ring mode #5 in case of unattached plates, frequencies of cavity mode (A), corpus bending modes (CBR), main body resonance (B), dominant frequency (extracted using Fast Fourier analysis from the sound signal) and quality factor which corresponds to dominant frequency. The change in the dynamic behavior of the plates during the manufacture of violins was statistically investigated using Discriminant Function Analysis. The research results showed that the top (spruce wood) and back plates (maple wood) have a very different vibrational behavior from each other due to wood species features. Changing the thickness of the plates by ±0.6 mm compared to the reference thickness leads to changing the frequency response of the back plates (maple). The thinner the plates, the more obvious the difference between the top and the back plate is, in terms of the maximum frequency. The stiffening of the plates mainly affects the quality factor of the sound oscillation damping, and the addition of the neck reduces the quality factor. Dynamic rigidity and frequency in cavity mode react most quickly to changes in plate thickness.
... Regarding the soundboards, there are many factors that affect their vibrational behavior, such as the geometrical characteristics (arching, thickness and distribution of thicknesses), the material properties and the anisotropy and inhomogeneity of the materials. In the literature, after the pioneering experimental work of Hutchins [41] there are various studies [42][43][44][45][46][47][48] that numerically study the violin free top and back plates, providing valuable guidance to violinmakers on the aforementioned factors that influence the plate frequencies and mode shapes before the final assembly on the instrument. Molin et al. [48] investigated the influence of the overall plate thickness variation, local thickness variations, arching height and material parameters, while experimental measurements of Chladni patterns were used for comparison with the FEM results. ...
String instruments are complex mechanical vibrating systems, in terms of both structure and fluid–structure interaction. Here, a review study of the modeling and simulation of stringed musical instruments via the finite element method (FEM) is presented. The paper is focused on the methods capable of simulating (I) the soundboard behavior in bowed, plucked and hammered string musical instruments; (II) the assembled musical instrument box behavior in bowed and plucked instruments; (III) the fluid–structure interaction of assembled musical instruments; and (IV) the interaction of a musical instrument’s resonance box with the surrounding air. Due to the complexity and the high computational demands, a numerical model including all the parts and the full geometry of the instrument resonance box, the fluid–structure interaction and the interaction with the surrounding air has not yet been simulated.
