Violins have attracted much interest of many acoustic engineers or researchers compared with the other instruments because of their beautiful sound, shape and their complex structure. In this study, the characteristics of sound produced by violins were investigated based on acoustics and vibration technique. Time and frequency domain of acquired sound pressure were investigated between a fabricated bowing device to keep a bow constant speed and a professional player of violins. Modal analysis for the violin was conducted under two boundary conditions. In order to obtain high frequency response function, the swept excitation using a sound source was conducted. The frequency response function and the modal shape were compared between two conditions.

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As sound quality of a classical guitar, Length of a sound is affected greatly by damping of sound pressure in chronological order. In addition, the characteristics are different in a frequency domain. In consideration of both, we suggest compound evaluation sheet of sound quality

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Front soundboard of classical guitar is the most important as part giving a sound. Because, it emit many sound energy. And, sound board has braces to reinforce it. We examined a difference of bracing pattern by investigating a vibration characteristic and an acoustic feature.

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This paper investigates the application of Statistical Energy Analysis(SEA) to a rotary machinery system. Since such the machinery is composed of structures that mode counts are very low, the application of SEA is severe then the Energy Analysis Model(EA model) is tried to be applied. First, the vibration characteristics of the rotary machinery with three specifications are measured. Then, our process for reducing the vibration using SEA is applied to them for building SEA and EA models and identifications of power input during operations. As a result, the differences of vibration characteristics on the three specifications can be described by the process.

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The objective of this paper is to investigate influence of in-plain vibration on SEA models building. First, compliances of in-plain longitudinal and out-of-plane bending vibrations on two elastic beam system is discussed. Next, analytical SEA approach and FEM calculations are performed to compare the SEA models with and without in-plain subsystems. In analytical SEA, out-of-plane energy without in-plain subsystems becomes bigger compared to out-of-plane energy with in-plain subsystems as the frequency increase. In the SEA model using FEM, in-plain energy becomes bigger only the frequency with in-plane longitudinal modes.

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This report deals with two-dimentional FEA for deformations and vibration damping in laminates including Biot type porous materials. In this analysis, particle displacement vectors for internal air in the porous material are adopted as unknowns for the discretized equations for FEM. And displacement vectors for frame in the porous material are also selected as the unknowns. A numerical code is developed. For numerical examples, Biot type porous material is sandwiched between two viscoelastic layers (i.e. a damped steel beam and a plastic sheet), and then, responses of the laminates are calculated. Influences of conditions at the interfaces between the frame of the porous material and the viscoelastic layers on distributions of deformations in the responses are clarified.

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Vibration and acoustic models for carpet on automotive vehicle floor has been developed. The vibration model is expressed of by lots of sets of a spring, mass and damper on FEM model. Two kinds of the acoustic models are developed for the two types of carpet with and without bucking sheet. These models on a beam structure are verified by the comparison of the modal properties, frequency response and acoustical intensities between measured and calculated. These models are also applied to a plate system. As a result, the predicted results are good agreement with the measured on the vibration of both the panel and the carpet surface, radiated sound.

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The purpose of this study is to develop an anti-howl back device in karaoke. An acoustic feedback path of such a microphone speaker system is generally varing when the microphone is moving. Then the impulse response was instantaneously estimated by the LMS algorithm, using music source. The feedback signal was canceled by an adaptive filter which realized the impulse response. By using this system, the acoustic feedback was proved to be attenuated. But some important issues remained.

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We examine convergence characteristic of the LMS algorithm in an improved ANC system for cancelling beat noise. We also perform numerical simulation of the adaptation of the system in order to test analysis results. As a result of calculation of the condition number of the correlation matrix of a reference signal, the value of the condition number becomes smallest when the sampling frequency is 4 times of fundamental frequency of noise. If a value of the condition number is small, the convergence speed becomes fast. As a result of numerical simulation, the tendency that is similar to an analysis result is shown.

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The purpose of this study is about noise reduction by Active Noise Control at the opening with a louver which installed Piezoelectric Vibrator. From the viewpoint of improvement of appearance and privacy, louvers are used at large opening aimed for air conditioning and ventilation. In late years, in a house and an apartment, a leak of a sound from the opening which installed a louver becomes a problem. The experimental results show that noise reduction is obtained from 5dB to 30dB at control point by ANC system.

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In 3-dimensional sound field, it is difficult to control noise in whole area. Instead of whole area control, the controlled area can be followed to people in that field by new approach proposed in this paper. In the proposed algorithm, FTF algorithm that has fast converging property is introduced to a direct adaptive algorithm which does not need an error path characteristic. A numerical simulation is carried out with a sound field that the error microhpne moves during control. Experiments are also carried out under several conditions. From the results of the simulations and the experiments, the effectiveness of the proposed algorithm is shown.

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The possibility of a concept of active sound cancellation control based on the wave absorbing principle of conventional railway wheel/rail rolling and impact noises by on-vehicle-type devices was examined. First, theoretical simulations on the basis of BEM were executed, and then the experiments of active noise control were carried out by using multi-device-units installed on the panel system simulating the floor/side wall of railway cars, where both the simulated random rolling noise and impact noise measured in the real field were used. As a result, it was verified that the sound cancellation effects are actually observed over the relatively broad seeable space from the rail, showing the validity of the proposed concept.

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This work deals analytically with the optimal design of dynamic absorber for quenching squeal generated in car disk brakes. In previous our work, the analytical model of car disk brake squeal was developed. In this paper, the dynamic absorber is attached to this model, and the controlling effect of squeal of the dynamic absorber is presented. From analytical results, optimal parameter of damping ratio, the natural frequency, and the effect of mass ratio of dynamic absorber is established. Moreover, the relationship between the attachment position of dynamic absorber and the effect of that is investigated.

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This paper deals with the occurrence mechanism of the squeal phenomena generated in a new type of a bicycle disk brake unit and its countermeasure experimentally and analytically. It was made clear that the squeal was in-plane vibration in the direction of a disk surface with frequency 650 Hz caused by frictional characteristics with negative slope with respect to the relative velocity, and was generated in the vibration system including the brake unit and spokes, in the same manner of an old type of disk brake unit. The simple analytical model of the bicycle disk brake system was set up. Some features of the squeal phenomena were made clear analytically and it was confirmed that the analytical results agreed well with the experimental ones.

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This paper describes the multi-objective optimal design of frame structures using genetic algorithm and generalized transfer stiffness coefficient method(GTSCM). The GTSCM has been developed as a method of vibration analysis with high performance and easiness of application. The topology optimization procedure for minimizing total mass and maximizing first natural frequency is developed based on the ground structure approach. The computational amount for calculating the objective functions can be minimized by utilizing the GTSCM. Optimal design example is provided to confirm the effectiveness of the present method.

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Vibrations of a rotating circular membrane under distributed load are investigated. Bending stiffness is ignored and von Karman theory is applied to formulate equilibrium equations and vibration equation around the equilibrium states. The equations are numerically solved taking account of buckling and vibration modes are obtained. The result is shown to be consistent with vibration modes of a spring-mass system which simulates elasticity of membrane. An experiment of a rotating circular membrane under gravity in vacuum is carried out and a vibration mode is found to agree with the vibrations observed when high rotation frequencies.

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If a machine in operation has a fault, sings of the fault appear in a monitored signal and are usually synchronizing with the operating speed. In this paper, harmonic wavelet is utilized to detect the minute signs of faults in the signal. The signal of a machine element in ordinary operation is regarded as nearly periodic. It is important for the detection of the signs to reduce the noise and the edge effects in the signal. Useful methods to reduce the noise and the edge effects are devised. Moreover, the signal plane was studied, and the signs were detected clearly.

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In view of the latest trend of the fractional derivatives and its worldwide practical use, the history of researches on the fractional derivative and its applications are brifly reviewed. Since the authors require efficient numerical solution methods to solve nonlinear fractional differential equations(NFDEs), a numerical integration algorithm for NFDE is developed by means of Newmark-β method. The performance of the developed algorithm is firstly investigated and then a typical NFDE is solved to study the nonlinear behavior of the NFDE in terms of the numerical solution. A useful new integration algorithm to solve the NFDE is then proposed.

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This paper is concerned with the development of an efficient algorithm for the numerical solution of the fractional differential equation(FDE). The numerical integration of the FDE needs significant computational cost, because the fractional convolution integral included in the fractional derivative, requires O(N^2) operations for N points calculation. The kernel of the fractional integral has singlarity and consequently excessive small time-step near the singularity is needed to secure the high precision in the numerical calculation. This difficulty is solved to propose a new computational procedure for fractional derivative by introducing the variable trasformation from the physical time to the power time which is newly defined in this paper. The proposed algorithm is used to solved the nonlinear FDE. Computational results are compared with those by the former method (Nasuno and Shimizu, JSME (C), 2006). The proposed method shows remarkably higher performance than the former one.

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Analytical results are presented on nonlinear vibrations of a post-buckled clamped beam constrained by an axial elastic spring subjected to combined axial-and-lateral excitations. Equations of the motion of the beam are derived including the term of parametric excitation due to the axial excitation. Nonlinear periodic responses are calculated with the harmonic balance method. Time progress of the beam, including non-periodic response, is calculated with numerical integration. Effects of the amplitude and phase of the axial excitation are carefully examined on the responses of the beam. It is found that transitions between non-resonance, principal and non-periodic responses are sensitive to the amplitude and phase of the axial excitation, which suggests a possibility of control on chaotic response.

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The characteristics of two nonlinear vibration absorbers simultaneously attached to structures under harmonic excitation are investigated. The frequency response curves are theoretically determined using Andronov and Witt's method. It is found from the theoretical analysis that pitchfork bifurcations may appear on a part of response curves which are stable in a system with one nonlinear dynamic absorber. Three steady state solutions with different amplitude appear just after the pitchfork bifurcation. After that, Hopf bifurcations may occur depending on the values of the system parameters and amplitude modulated motion including a chaotic vibration appears after the Hopf bifurcation. The Lyapunov exponent is numerically calculated to prove the chaotic vibration. In addition, it is also found that only Hopf bifurcations, not pitchfork bifurcations, can occur even when the linear and nonlinear dynamic absorbers are combined.

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Nonlinear whirling motion of a tower-like structure carrying a cylindrical tank partially filled with liquid is investigated when the structure is subjected to only horizontal harmonic excitation. When a ratio 1:1 of the tuning condition is satisfied between the natural frequencies of the structure and sloshing in the liquid tank, modal equations are derived considering the nonlinearity of the hydrodynamic force. Then, frequency response curves are theoretically calculated by using Andronov and Witt's method. They show that whirling motion and chaotic motion of the structure may occur depending on the frequency and magnitude of the excitation, because the swirl motion and amplitude modulated motion through Hopf bifurcation appear in the tank. These results were also observed in the experiments.

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Experimental results are presented on chaotic oscillations of a shallow shell-panel with a concentrated mass. The results are compared with the results for the shell-panel without a concentrated mass. The shell-panel is excited by periodic acceleration laterally. Chaotic responses are generated in specific regions of the exciting frequency. The chaotic responses are examined with the Poincare projections, the Fourier spectrum and the maximum Lyapunov exponent. The Lyapunov exponent of the chaotic response of the shell with the mass takes smaller value than that of the shell without a mass. Contribution of modes of vibration to the chaotic response is analyzed with the principal component analysis. The chaotic oscillation involves dynamic snap-through response. Moreover, the chaotic response of the shell involves more than three modes of vibration simultaneously. The patterns of the vibration modes which contributes to the chaotic responses are transformed by the concentrated mass.

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This paper presents a procedure to derive reduced-order nonlinear equations using the projection onto the sub-space which includes a solutions of whole-space equations in approximation. Nonlinear finite element(FE) equations are derived by the principle of virtual work taking into account geometrical nonlinearity. Reduced-order equations are derived by the projection onto the space defined by vectors that are obtained by solving static nonlinear FE equations on which equivalent inertia force is acting and by decomposing the solution vectors of the static equations. Reduced-order equations for straight beam and curved beam are derived, and numerical results about the fundamental natural frequency show good agreement with those obtained by applying a numerical integration directly to the equations in the whole space.

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This paper describes an experimental study on self-excited vibration of a vibrating screen classifier. We investigate the motions of granular material, the effects of frequency of forced vibration and mass of granular material in the vibrating screen classifier. Consequently, self-excited vibration is observed.

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Spatial motion Spherical pendulum satisfies condition of one-to-one internal resonance, and it is reported by theoretical studies that complex phenomena including chaos occur. In this paper, spatial motion of a spherical pendulum excited harmonically at the pivot is investigated experimentally. It is found experimentally that spatial motion of spherical pendulum occurs near the primary resonance point, and chaos motion occurs, too.

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The 1/2-order subharmonic resonance occurs when the rotational speed is in the vicinity of twice the natural frequency. Jeffcott Rotor used basically and widely in the analysis of resonancies is a two-degree-of-freedom model with a deskat the midspan of a massless-shaft. For the above condition on the rotational speed, we clarify the nonlinear characteristics of the resonance in horizontally supported Jeffcott Rotor. Applying the method of multiple scales, we directly derive the amplitude equations for the forward and backward whirlings and depict the relationship between the rotational speed and the response amplitude. Furthermore, experiments are performed and the results are compared with the theoretical ones.

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The relationship between the self-synchronized phenomena of rotator-type oscillators and the nonlinear modes of the system is investigated analytically. The self-synchronized phenomena and the nonlinear modes in two systems constructed from DC motors are analyzed by applying the shooting method. In this report, the periodic motion of the nonlinear undamped autonomous system is regarded as a nonlinear mode. Some calculated results clarify that the self-synchronized phenomena correspond well with the nonlinear modes including the stability and that some differences between their characteristics result from the effects of the damping.

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The purpose of this study is to identify modal parameters of an elevator car by operational modal analysis, and to estimate the stiffness parameters of guide devices. The frequency range of interest is up to 5 Hz, where the assumption that the car behaves rigidly is valid. In order to check the assumption the Rigidity Indicator Function(RIF) is defined as a function of frequency. FDD(Frequency Domain Decomposition) method is used for the operational modal analysis. The stiffness parameters are estimated by minimizing the error between the natural frequencies of the modal model and those of the analytical model.

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Mode contribution is often utilized to analyze system dynamics. However, it may be dispersed over a large number of modes and difficult to understand for system dynamic characteristic with high mode density. New method is developed to solve this problem including such system where recurring deformation modes (principal modes) are extracted by performing singular value decomposition on deformation patterns of the response. By using this method, the systems can be modeled with substantially smaller number of degrees of freedom compared to the modal solution. The method offers on more efficient approach for analysis of systems with dense modes.

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In vehicle systems or construction machinary occupational drivers might expose themselves to vibration for a long time. This may cause illness of the spine such as low back pain. Therefore, it is necessary to evaluate the influence of vibration to the spinal column. For the purpose, the vibration experiment is conducted, and the response of the spinal column is measured in detail. Modal parameters of upper human bodies are identified by using measured transmissibilities. As the results, three modes are observed in 4Hz to 20Hz. Additionally, the average method of human transmissibilities is examined.

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The method was established to identify the dynamic stiffness of the engine mount using modal parameters acquired from experimental modal analysis. Vibration test were conducted using actual large outboard motor the BF225(165kW), and the dynamic stiffness of the mounts was identified. The results show that this method can identify the engine mount dynamic stiffness more adequately than the conventional method, even when the engine mounts are subjected to loads corresponding to thrust force or even in the case that the stiffness of the parts supporting an outboard motor is low.

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In this paper, the authors present an experimental modeling of an actual outboard engine, whose rigid body properties and dynamic characteristics up to 400 Hz are both to be expressed in the form of spatial matrices by the experimental spatial matrix identification method. To verify the basic validity and usefulness of the modeling based on the experimental identification, the test outboard engine is identified under detaching its flywheel. A set of spatial matrices are obtained in the condition. Then, the dynamic characteristics of the test engine under attaching its flywheel is predicted by computation. The natural frequencies and their associated natural modes are predicted with practically good accuracy.

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This paper presents vibration test and dynamics modeling of an automotive suspension system. Concretely, the vibration tests are conducted in three translational directions, and in several kinds of input levels. The dynamical modeling by MBD is carried out base on the experiment. It is shown that the vibration level dependency is explained by changes of the equivalent stiffness and damping coefficients at the shock absorber. An analytical example by the constructed model is also shown with respect to the level dependency.

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Recently, baseball bats that have kinds of characters have been marketed due to advances in the materials and structure of modern baseball bats. One of remarkable point is a sweet spot in bats. But a sweet spot is sensuous and its point is laxness. So the reason why a sweet spot is approved is researched in this study. First of all, the first node, the second node and center of impact were measured. Next, the ball was made to collide with them and the repulsion coefficients were measured, and compared.

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This paper presents an analytical model for the prediction of piston secondary motion and the vibration due to piston slap. For the modeling of piston slap phenomenon, cylinder liner is modeled as a several spring-mass system that are connected by modal characteristics, and lubricant film between the piston and the cylinder is modeled as reaction force vectors which excite resonant mode of them. By comparing experimental results and analytical ones, the validity of the proposed model has been confirmed. Furthermore, it was applied this analysis to transverse-mounted 4-cylinder engine, and was revealed the transient response to cylinder wall by piston slap.

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This paper describes a decomposition method for structural intensity on structures into intensity component expressed by a natural mode. Firstly, the formula of the method is derived from the modal description of vibration displacement. This method is based on the capability of displacement expression by using the summation of the real parts each modes and the imaginary part of the only resonant mode under the excitation frequency is near the resonance. It is numerical demonstrated that the method gives each intensity component on a beam or a plate at a near resonant frequency.

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This paper proposes the noise reduction approach of the acoustic power radiated from mechanical structures based on Acoustic Power Mode concept. The derivation of the Acoustic Power Mode of general structures is formulated, and the structural modification using the Acoustic Power Mode is presented. Firstly, Acoustic Power Matrix is derived by using FEM and BEM. The structural modification using Acoustic Power Mode is examined, and the modification method is presented in order to decrease of sound power efficiently. Lastly, the sound power could be decreased even though vibration is increased under a certain condition.

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Observing each vibration mode is a basic and useful approach for automobile NVH in the booming noise frequency range. In the recent vibration analysis, the number of modes in the target frequency range increases as the finite element model reflects an actual automobile faithfully. In this case, it's difficult to examine individual mode, and it is required a lot of time to establish effective countermeasures. In this study, a practical method is proposed to raise the efficiency of analysis by grouping these modes into several types. The types are defined by the similarity of the effects of modifications that are made on noticed portions of the structure. The grouping method enables the analyst to effectively draw countermeasures for each group and reduces the analysis time.

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A method for predicting impulse responses on structures based on vibration energy is discussed. One of these methods is Transient Statistical Energy Analysis(TSEA). First this paper discusses the behavior of shock response predicted by TSEA. Next it is discussed that the TSEA can be applied case for 2 degree of freedom system. Then it is shown that the predictions by TSEA are compared with the exact responses of the system. Moreover an exact energy flow equation is derived from the exact solutions of the system in order to discuss the basic equation of TSEA.

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This paper describes the necessary requirements for self-identification, which has been proposed as a structural identification with variable structural parameters of adaptive structure systems. Also, a generalized control vector is defined to express the modal force consisting of eigen-values and eigen-vectors and given structural matrices of the specific vibration modes. The controllability and observability of the eigenspace of the adaptive structure systems are introduced to derive the requirements using sensitivity analysis of eigen-value and eigen-vector with respect to the generalized control vectors. Finally, numerical examples of self-identifiable and not self-identifiable systems are shown, respectively.

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This paper proposes a procedure for the analysis of the natural frequencies of finite element models with uncertain parameters. The uncertain model parameters are modeled as fuzzy numbers and then the uncertain natural frequencies are calculated by a fuzzy approach based on interval arithmetic. To reduce the computing effort in the interval arithmetic, the response surface method is used instead of the vertex method. The examples show that the proposed procedure produces accurately the membership function of the natural frequency from the response surface model. The influence of the variation of model parameters on the variation of natural frequencies is easily evaluated from the results obtained by the proposed fuzzy analysis procedure.

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Spatial filter whose importance has been recognized is useful for suppressing modal observation spillover and making reduced-order model of the structures. The authors have proposed a design method of spatial filter of structures. A small number of sensors are used to design spatial filter that are below number of the modes in target frequency range. In this paper using the experimental modal vectors redesigns the temporary spatial filters based on the analytical modal vectors. This paper installs the evaluation of optimal sensor position for establishing spatial filter. The workability of the method is investigated by experimental application to a cantilever beam.

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Vibrations of a rotor supported by a repulsive type passive magnetic bearing are investigated. The restoring force of a repulsive type magnetic bearing is calculated numerically. Then, this obtained restoring force is approximated by the cubic power series expression. The influences of magnet length and discrepancy between inner and outer magnet positions are investigated. The system shows hard spring characteristic when the difference between the length of inner magnet and outer magnet is small, while the system shows soft spring characteristic when the difference is large. Furthermore, the system shows hard spring characteristic when the discrepancy between inner and outer magnet positions is small, while the system shows soft spring characteristic when the discrepancy is large.

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Because the magnetic force has nonlinear characteristic, nonlinear phenomena may occur in the rotating machinery supported by magnetic bearings. Therefore, the investigations of vibration phenomena are important for prevention of the vibration problems. In this paper, a rotating shaft system supported by magnetic bearing is modeled by taking into consideration the PI control characteristics of amplifier and delay characteristic of magnetic force for the control electric current. The nonlinear analysis is performed and influences of these dynamical parameters of control system on the vibration phenomena of rotor system are clarified.

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In order to calculate high-speed transient phenomena of a rotor-system such as rotor collision with stator due to blade loss, a very small incremental time step is required in the integration. But a small time step is known to cause a numerical instability when a direct integration such as Newmark-β method is applied in terms of physical coordinate. This paper presents a method using constraint real mode synthesis in which modes are derived from neglecting gyro-moment and fixing bearing connection freedoms to be zero. This method is proved to be highly stable and also to have good accuracy and efficiency.

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Floating bush journal bearings are widely used to support very high speed rotating machineries. The bearing has a thin bush inserted between the journal and the bearing housing. The rotating shaft is supported by two oil films formed in the inner and the outer clearances of the bush, when the lubricating oil is supplied to the bearing. The bearing is widely known to show the peculiar phenomena, that is, the decrease of the bush-to-shaft speed ratio and the disappearance of the oil whip. The effects of the bearing load and the viscosity of the lubricating oil on the phenomena are cleared experimentally.

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This paper proposes the expansion of application of the damper bearing for small and medium sized rotating machinery. The new damper has a compact size that enable standard design combined with rolling element bearing. A new design of the damper is presented. The new design consists of thin ring and special patterned wire cut grooves. The design analysis and experimental study are presented. The dynamic tests were carried out for this model damper with cavitations effects. Test results showed the sufficient damping effect for actual applications.

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A clearance configuration of fluid-film journal bearings is optimized in a sense of enhancing the stability of a full circular bearing at high rotational speeds. A performance index is chosen as the sum of the squared whirl-frequency ratios over a wide range of eccentricity ratios, and a Fourier series is used to represent an arbitrary clearance configuration of fluid-film bearings. An optimization problem is then formulated to find the Fourier coefficients to minimize the index. The designed bearing has a clearance configuration similar to that of an offset two-lobe bearing for smaller length-to-diameter ratios. It is shown that the designed bearing cannot destabilize the Jeffcott rotor at any high rotating speed for the wide range of eccentricity ratio.

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Partial admission has been applied to steam turbine because it produces high turbine efficiency at low loads. The shock load caused by partial admission generates excitation force on a blade, and the vibratory stress of the blade may become a cause of HCF. Therefore, in designing a steam turbine blade, the vibratory stress caused by partial admission should be exactly predicted. This paper, first, presents the analysis method to calculate the vibratory stress of the blade caused by partial admission. And the vibration response characteristics to shock load is explained, using some calculated results of simplified blade models. Secondary, the response analysis is carried out for the actual grouped blade and the integral shroud blade, and the results are evaluated from the viewpoint of blade reliability.

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