Violin Bridge Research Articles

기구학 해석을 이용한 바이올린 활 연주 로봇팔의 최소 링크 길이 계산

For a violin playing robot to be successful as an entertainment robot it needs to portray the image of a human arm playing the violin. Hence it is desired that the robotic manipulator has an articulated structure similar to the human arm. Since shorter link lengths result in smaller link weight, smaller actuator size/weight, and thus fast motion capabilities of the manipulator, it is crucial to determine the minimum link lengths of the manipulator. This paper presents a computation method of the minimum link lengths required for the bow motion and the kinematic design of the violin bow playing robot arm. The workspace of the bow playing arm is analyzed using the geometric dimensions of the bow and the violin bridge. The bow frog motion paths are computed for four violin strings. It is shown that a planar RRR mechanism can generate the motion required for violin bow playing robot, and the minimum link lengths of the manipulator are found that result in the robot workspace encompassing the bow frog motion paths and that avoids the singularities in the robot motion path.

Bridge shapes of the violin and other bowed instruments, 1400–1900: the origin and evolution of their design

Abstract As one goes back in time, the number of extant bowed instruments decreases gradually, and this is particularly true for loose parts such as bridges, pegs and tailpieces. The current article traces the development of bridges of instruments of the violin family, based on a study of extant instruments and around 800 iconographic sources. This study reveals the origins of the various elements of bridges found on modern instruments of the violin family, and reconstructs the different stages of their evolution. Many elements of the modern violin bridge were already present, sometimes hidden, in bowed-instrument bridges of the 16th century. The extensive appendices and many line drawings offer today’s researchers, makers and restorers the possibility of providing historically informed bridges that are less fantasized than those hitherto often encountered on restorations or reconstructions of old instruments.

The Influence of Wood Modification on Transfer Function of a Violin Bridge

The violin bridge is an important component of a violin since it transmits the excitation forces from the string to the violin body. Depending on its structure, at a certain frequency spectrum, the bridge acts as a damper or amplifier of excitation forces, which depends on its transfer function. In the study, transfer functions in the range from 400 Hz to 7000 Hz in vertical directions of 3 bridges were measured. The bridges were made from maple wood and supplied by different manufacturers. The bridges were then thermally modified, and the transfer functions were measured again. To determine the influence of thermal modification on material properties, a sample of maple wood was also modified together with the bridges, and the modulus of elasticity and shear modulus before and after the modification were measured. Using Ansys software, a bridge was modelled by the finite element method, by which natural frequencies and transfer functions before and after the modification were calculated. It can be confirmed from the research that wood modification influences the bridge transfer function and that the finite element method can be used to determine the dynamic properties of the bridge by knowing the wood material properties and, therefore, to predetermine the transfer function of the violin bridge before its production.

An approach to construct a three-dimensional isogeometric model from μ-CT scan data with an application to the bridge of a violin

We present an algorithm to build a ready to use isogeometric model from scan data gained by a μ-CT scan. Based on a three-dimensional multi-patch reference geometry, which includes the major topological features, we fit the outline, then the cross-section and finally the three-dimensional geometry. The key step is to fit the outline, where a non-linear least squares problem is solved with a Gauss-Newton approach presented by Borges and Pastva (2002). We extend this approach by a regularisation and a precise interpolation of selected data points. The resulting NURBS geometry is ready for applying isogeometric analysis tools for efficient numerical simulations.As a particular example we examine the scan data of a violin bridge and present the complete workflow from the μ-CT scan up to the numerical simulation based on isogeometric mortar methods. We illustrate the relevance of the constructed geometry with a vibro-acoustical application.

Modeling, identification, and optimization of violin bridges

AbstractWe present the derivation and implementation of a mathematical model for the linear elastic structure of a violin bridge. In favour of getting highly accurate simulation results, special effort has been taken to reconstruct the computational geometry from a µ‐CT scan. After laying out our approach for this in detail, we also present first vibroacoustical analysis like solving the eigenvalue problem of elasticity for the orthotropic material law of the wooden bridge and simulation of its dynamical behaviour. We then conclude with explaining our ongoing work of identifiying material paramters by an inverse problem. With this project we are aiming to optimize a violin bridge regarding its material parameters and its shape.

Anomalie de rotation rénale entraînant une hydronéphrose géante prénatale

We report the case of a malrotated right kidney associated with giant prenatal hydronephrosis due to a non vascular extrinsic ureteropelvic compression. The kidney presented an hyper-rotation of 180° in relation to the original fetal position, with the renal hilum backward looking. At neonatal surgery we discover that the inferior pole of the kidney pushes laterally the ureteropelvic junction like a violin bridge. The simple uncrossing of the ureteropelvic junction from the inferior renal pole relieves the extrinsic ureteral obstacle and the giant hydronephrosis. The authors summarize the morphogenesis of the upper urinary tract which allowed to understand this rare anatomical variation.

Photoelastic Observation of Violin Bridge

Photoelastic Observation of Violin Bridge

Non-impulsive signal deconvolution for computation of violin sound radiation patterns and applications in sound synthesis

This work presents a method to compute violin body impulse responses (BIR) based on deconvolution of non-impulsive signals. This newly conceived approach is based on a frame-weighted deconvolution of excitation and response signals. The excitation, consisting of bowed glissandi, is measured with piezoelectric transducers built into the violin bridge and the response is measured as sound pressure with microphones. Based on this method, several research works have been carried out in the areas of acoustics and sound synthesis. First, by placing multiple microphones at different angles around the violin, we were able to compute a dense grid of 3D sound radiation patterns without restrictions in the frequency range. Second, the computed BIRs can be convolved with a source signal (captured with the same bridge-transducer and using the same violin), obtaining a highly realistic violin sound very similar to that of a microphone recording. The multiple impulse responses at different directions make has been used to enhance sound synthesis with spatialization effects. Finally, a bowing machine was built to perform repeatable glissandi and therefore be able to compute BIRs across different violins. The bowing machine has been used to compute cross-BIRs that map the pickup signal of electric violins to the radiated acoustic sound of acoustic violins, which allows to imitate the sound of any measured acoustic violin with an electric counterpart.

Indirect Acquisition of Violin Instrumental Controls from Audio Signal with Hidden Markov Models

Acquisition of instrumental gestures in musical performances is a field of increasing interest with applications in different areas ranging from acoustics and sound synthesis to motor learning or artistic performances. Direct acquisition approaches are based on measurements with sensors attached on the instrument or the performer, a process that usually involves the use of expensive sensing systems and complex setups that are generally intrusive in practice. An alternative is the indirect acquisition without sensors based on analysis of the audio signal. This paper reports a novel indirect acquisition method for the estimation of continuous violin controls from audio-signal analysis based on the training of statistical models with a database of previously recorded violin performances. The database contains synchronized streams of audio features and instrumental controls. Audio signal was captured with a vibration transducer built into the violin bridge, and instrumental controls were measured with sensors. The controls include bowing parameters (played string, bowing velocity, bowing force, and bowing distance to the bridge) as well as fingering position. Once the model is trained for a specific violin, we can perform indirect acquisition from analysis of the signal captured with its embedded transducer without the need for the sensors any more. The statistical methods used are Hidden Markov Models (HMM) with observation distributions parameterized as Multivariate Gaussian Mixtures (GM). HMMs provide a means for note recognition and following and parameter prediction is based on GM regression. Results show that the presented method constitutes an accurate, non-intrusive and low-cost alternative for instrumental control acquisition of a previously calibrated violin and recording device.

20902 ヴァイオリンの駒と表板の衝突モデルの基礎検討

This research aims at the learning from analysis of structure violin of a process for solving noise and vibration problems on machinery. Previous research has found the power input to the front plate through the bridge is in inverse proportional to the square root of frequency. This is same as theoretical infinite beam structure. It is hypothesized that nonlinearity causes similar phenomenon as infinite beam. We need to discuss impact modeling between bridge and front plate of violin. In order to discuss the modeling, two rigid mass connected with nonlinear spring is considered in this paper. Validity of our deduced model is examined with experiment result. As a result, the impact modeling is constructed in the Duffing's equation of nonlinear vibration system.

Violin Bridge Mobility Analysis under In-Plane Excitation

The vibration of a violin bridge is a dynamic contact vibration with two interfaces: strings-bridge, and bridge feet-top plate. In this paper, the mobility of an isolated bridge under in-plane excitation is explored using finite element modeling based on the contact vibration model. Numerical results show that the dynamic contact stiffness in the two contact interfaces has a great impact on the bridge mobility. A main resonance peak is observed in the frequency range of 2–3 kHz in the frequency response of the isolated bridge when the contact stiffness is smaller than a critical threshold. The main resonance peak frequency is affected by the contact stiffness as well. In order to verify the numerical findings, a novel experimental system is then designed on the basis of a piezoelectric dynamometer for bridge mobility analysis. Experimental results confirm the impact of the dynamic contact stiffness on the bridge mobility.

Experimental and Numerical Studies of Violin Bridge Vibration Mechanism

A violin bridge kept in place by the pressure of the four strings has a powerful effect on the tone of the instrument. Its dynamic mechanical behaviors are investigated using finite elemental modeling and experiments in this paper. Modal and frequency response analysis of an isolated bridge are carried out. Numerical results show that the frequency responses are related to the vibration modes of the bridge. Particularly, the bridge hill is due to the bridge itself, and linked to the in-plane rocking mode of the bridge near the bridge hill peak. Three-dimensional dynamic forces exerted to the violin plates by the strings and bridge are then experimentally measured using a dynamometer. The experimental results are then analyzed and correlated to the simulation. The frequency response analysis of an isolated bridge is demonstrated to be a potential tool to study the mechanical behaviors of the violin bridge.

Topology optimization for a frequency response and its application to a violin bridge

The main role of a violin bridge is to hold the strings and to transmit the vibration of the strings to the violin body. Violin makers have been empirically aware of the fact that a bridge is an important element which influences violin timbre. Thus, a bridge can be regarded as a mechanical filter in the transmission and be used to compensate weak or too strong areas in the resonance of the violin body. The filtering characteristics of a bridge depend on the geometry and material distribution of the bridge. In this paper, the sensitivity of band-averaged frequency response with respect to geometric design variables is derived. Then, topology optimization is applied to obtain optimal violin bridges for desired filtering characteristics. Numerical results show that the proposed optimization process can be a viable tool to design a bridge according to prescribed characteristics for musical performance.

Coupling of violin bridge modes to corpus modes analytical model

The transmission of string vibration forces to the violin belly by the bridge is modulated by two principal bridge resonances around 3KHz and 6 KHz, frequency bands critical to tone perception by the human hearing system. Much music acoustics research has dealt with these bridge modes (and those of the ‘cello and bass) and their influence on the excitation of the corpus modes at the bridge feet. This analytical treatment of the string to corpus transmission by the bridge is necessarily complex, but reveals factors in the process which explain the action of the different strings through the bridge and the levels of corpus mode excitation amplified by the bridge modes. The theoretical predictions are tested against experimental responses with normal bridges and bridges blocked to eliminate the two important modes.

Physical parameters of the violin bridge changed by active control

The physical parameters of a violin bridge have a significant influence on the tonal colouration of its sound. The resonance peaks of the bridge shape the response of the violin body. Reinicke and Cremer developed a simple bridge model that shows a typical broad frequency peak around 2.5kHz, because it incorporates the coupling to the violin body and the soundpost. By using the same model, Jim Woodhouse revealed the effect of some parameters of the bridge (mass, stiffness and foot spacing) on the instrument frequency response. Here the parameters of the violin resonance peaks are changed in real time, by applying an active control method. Such a technique, very useful in noise reduction, enabled to change separately the position and the shape of each peak of the bridge input admittance. On the bridge, 2 actuators and an accelerometer are placed at strategic positions in order to change the peak frequency and the damping factor values. The system behaviour is controlled by a Digital Signal Processor. Some sound results achieved with a real violin back up the theoretical equations.

The violin bridge as filter

The violin bridge filter role was investigated using modal and acoustic measurements on 12 quality-rated violins combined with systematic bridge rocking frequency f(rock) and wing mass decrements deltam on four bridges for two other violins. No isolated bridge resonances were observed; bridge motions were complex (including a "squat" mode near 0.8 kHz) except for low frequency rigid body pivot motions, all more or less resembling rocking motion at higher frequencies. A conspicuous broad peak near 2.3 kHz in bridge driving point mobility (labeled BH) was seen for good and bad violins. Similar structure was seen in averaged bridge, bridge feet, corpus mobilities and averaged radiativity. No correlation between violin quality and BH driving point, averaged corpus mobility magnitude, or radiativity was found. Increasing averaged-over-f(rock) deltam(g) from 0 to 0.12 generally increased radiativity across the spectrum. Decreasing averaged-over-deltam f(rock) from 3.6 to 2.6 kHz produced consistent decreases in radiativity between 3 and 4.2 kHz, but only few-percent decreases in BH frequency. The lowest f(rock) values were accompanied by significantly reduced radiation from the Helmholtz A0 mode near 280 Hz; this, combined with reduced high frequency output, created overall radiativity profiles quite similar to "bad" violins among the quality-rated violins.

Violin frequency response – bridge mobility and bridge feet distance

Good violins have a broad hill in the 2–3 kHz range of their frequency response. This hill has previously been attributed to the first in-plane resonance of the violin bridge. Experiments prove, however, that the hill is the result of two forces acting in opposite directions at the bridge feet. The experiments reported here show that the hill can be “tuned” by altering the distance between the bridge feet. It can be tuned both in terms of frequency and level but the properties of the violin cannot be neglected.

Comparison between Modern Violin Bridge and Baroque Violin Bridge by Photoelastic Observation and Frequency Analysis

A comparison between the modern bridge and the baroque bridge of the violin by photoelastic observation was carried out. The relationship between the stress part and the hole is symmetric in the modern and baroque bridges. The measured spectral envelopes of baroque bridges are similar to those of modern bridges in D- or G-strings, and have peaks at a frequency higher than those of modern bridges in E-string. The visualization method as used in this study may provide hints for the design of violin bridges.

Study on Bridge of Violin by Photoelastic Observation

The stress of the bridge of a violin was observed by means of the photoelastic method, and a frequency analysis of the tones of two violins was performed. It was found that the stress of the bridge and the tone of the violin depended on the shape and the tilt of the bridge, the direction of force applied by bowing and so on. In addition, it was demonstrated scientifically that adjustment of the instrument is very important and that players should maintain the instrument properly. The proposed visualization method may be helpful for violin teaching and for practice of bowing skills of amateur violinists.

Recent work and new axes of research for m o d a l y s, a sound synthesis program based on modal representation

modalys, developed at Ircam after 10 years for research and musical applications, is based on modal representation of vibrating objects, mechanical or acoustical. Modal data (natural frequencies, damping factors, and deflection shapes) are obtained from: (1) analytic modeling for simple structures as ideal string, cylindrical or conical open/closed tubes, rectangular plate with a simply supported boundary condition or violin bridge, ...); (2) experimental measurements for real structures with complex shapes (violin body, soundboard of piano, flute,...); and (3) finally by numerical methods (finite-element methods) which allow the creation of any arbitrary virtual shapes. The vibrating object involved is generally a set of simple and linear substructures. Nonlinearities, when they exist, are introduced in the coupling of substructures, for example reed and tube for the clarinet. Dissipation plays a critical role in the perception of some vibrating musical objects. The type of damping used in our modal representation is referred to as proportional damping (dissipation phenomena are in this case constant or proportional to the square of frequency). However, this type of damping may not apply in any case to the real objects. In this presentation, some sound illustrations on recent results of research and application development with modalys will be presented and discussed.