Magnetorheological compound (MR compound) was developed and its typical properties were investigated experimentally by using a rotational viscometer specially designed for MR suspensions. Magnetorheological fluid (MR fluid) is composed of magnetic particles and carrier oil. It is known as one of functional fluids, whose rheological properties can be controlled by the applied magnetic field strength. Utilizing these properties, brakes, clutches, dampers and various engineering applications have been studied. However, the sedimentation of the magnetic particles of MR fluid will result in unsteady dynamic behaviors of the MR devices. In order to reduce or avoid the sedimentation of the magnetic particles in MR fluid, Magnetorheological elastomer (MR elastomer) which is a functional solid material was developed. But, the amount of the property change decreased because the binding of the magnetic particles was too strong. As a new material for solving these problems, MR compound is proposed. This is adjusted the degree of crosslinking in the process of the addition of additives and molding after mixing the elastomer stock and the magnetic particles. The basic properties of MR compound haven’t yet been clearly elucidated because it is located in the region between the liquid and the solid. In this paper, it is the purpose to elucidate the magnetic field response properties of MR compound. The relationship of the strength of the magnetic field applied to MR compound, the shear rate, and the viscosity change were investigated experimentally. Also, states of sedimentation of MR compound and MR fluid were compared.

Particle dampers are enclosures partially filled with granular materials, attached to a primary system with high displacement amplitudes. Due to their effectiveness, simplicity and temperature insensitivity, they have been investigated extensively. The discrete element method (DEM) is often used to simulate the dynamics of particle dampers. Because of the very large number of particles in particles dampers, the main issue is the computational efficiency. Some computational approach which can run faster than the original DEM was proposed. However, the validity of the computational approaches has not yet been considered. In this study, a computational scheme combining the uniform grid with linear lists and the coarse-grain model is presented. The validity of the computational scheme is examined by comparison with experimental results. In addition, the relationship between the coarse grain ratio and the errors of the analysis is investigated.

Passive vibration dampers are very efficient solution for vibration control in structures with low natural frequencies. However, conventional dissipative elements used in their dampers require maintenance due to their nature of their function. Therefore, it is necessary to develop a virtually maintenance-free dissipative element. In this study, a tuned rolling-granular damper is presented. This damper consist of a cylinder partially filled granular materials, which rolls in a cylindrical surface attached to a primary system. In this damper, the granular materials is the energy dissipating agent. Granular motion induced inside the cylinder, consists of intermittent contacts with other particles and the wall of the cylinder. It results in the rapid energy consumption. The effect of the particle size and mass ratio on the damping performance was investigated experimentally. The granular materials used in this study were steel particles and are of uniform size. By means of the discrete element method (DEM), an analytical solution is provided to estimate the damping performance. The contact force acting on the rolling cylinder is modeled by the sum of the spring force based on Hertzian contact theory and the damping force introduced by Tsuji. Comparison between the theory and the experiment was found to be good.

This study was conducted for the purpose of establishment of the torque increase technique of the rotary particles damper. The steel balls of 0.8 mm in diameter and the sands of 0.25-0.30 mm in diameter were used as the particles. The dynamic flowability of the sands is lower than the fluidity of the steel balls. The torque properties of the rotary particles damper were investigated under conditions of frequency of 10 Hz from 1, and amplitude of 30 degrees. The torque of the rotary particles damper increased when the steel balls were used at a high packing fraction. However, many pulsatile torque changes occurred. On the other hand, the torque of the rotary particles damper using the sands was larger than the torque of the rotary particles damper using the steel balls. The rotary particle damper using the sands did not have the pulsatile torque changes.

We have studied the damping mechanism of a granular material damping system applied to reducing vibration in structures that have a high natural frequency and small vibration displacement. In this report, we considered the damping mechanism based on the vibration energy. We calculated the movement of the all granular materials and the container, the work by the collision, and the work by the friction. We compared them to container displacement. As a result, we obtained the conclusion as follows. The work by the collision between the granular materials and the container has a big influence on the damping mechanism when the total mass of granular material is small. On the other hand the influence of the work by the friction is increased in accordance with increase of the total mass of granular material.

The importance of passive vibration isolator is increasingly growing because of its stability of performance and lower cost. In the previous paper, the authors proposed a nonlinear passive isolator for vertical direction based on a post-buckled L-shaped beam, which consists of two thin plates, and the performance of the proposed isolator in post-buckled state of unstable buckling mode was numerically and experimentally investigated. Then, the following two undesirable characteristics were detected. Two resonance peaks, which correspond to the fundamental natural mode of the translational motion and the rotational motion of an isolated object, appear in low frequency range. The isolation range of the isolator is in the frequency range over the second natural frequency and the isolation performance is compromised by the presence of higher frequency internal resonances of the isolator. In this paper, we investigate the countermeasure against the second and higher natural modes to avoid the undesirable resonance. Concretely, we newly propose two isolation models to suppress the second and higher resonance and validity of proposed systems are numerically investigated.

This paper deals with the numerical analysis of an air spring that consists of two tanks connected by a long pipe. Two resonance points may appear in the frequency response of a vibratory system supported by this type of air spring despite the fact that the system has an apparent single mass. This phenomenon is caused by the presence of a secondary mass as reported in our previous paper. It was found that the secondary mass is the mass of air contained in the pipe. The magnitude of this mass is extremely small, but the acceleration of the air in the pipe ― and therefore the inertia force generated from it ― becomes very large. The generated force is further amplified by the Pascal’s principle and is transmitted to the supported mass. There are obvious nonlinear characteristics in this type of air spring; whereas the previous studies were based on linear assumptions. In this study, the governing equations for the air stream expressed by a nonlinear partial differential equation were solved by using the finite difference method. In particular, the pressure loss is evaluated due to air vortex being generated behind the orifice installed in the pipe. As a result of this study, it was found that the orifice is effective in suppressing the height of the secondary resonance point. Of course, it has become possible to accurately estimate the amplitude dependency of the dynamic characteristics of the air spring supported system by this non-linear analysis.

The vibration isolator discussed in this study consists of two rectangular plates with four air springs inserted between them. Each air spring has a main tank and reservoir tank connected by a small diameter pipe. Because this structure has week rigidity in the horizontal direction, guide shafts are provided to constrain the movement of the table only in the vertical direction. The guide shafts are supported by gas bearings to minimize sliding friction. Both the equivalent spring constant and the equivalent damping coefficient of the vibration isolator are generated by two of the cause. One is caused by the air flow, which can be calculated theoretically. The other is generated by the compression, expansion and sliding friction of the rubber membrane, which is impossible to calculate. The latter was measured experimentally. Thus, the frequency response of the vibration isolator system was calculated from a simplified expression. The calculation results are in good agreement with the eperimental values, and the correctness of our calculation method has been demonstrated.

Strong demand exists to reduce the noise in transformers for the sake of the environment. The noise of transformers can generally be reduced by increasing the size of the machines. However, this leads to increased costs, so a non-resonant design is needed for the transformer core, coil, and tank. This report, presents our investigation on the numerical analysis modeling method of the shell-type transformer tank. The results were that the numerical analysis model that modeled the tank and the oil flow channel could predict the natural frequency with an error of less than 12%.

This work presents a study to reduce interior noise of railway vehicle by suspending floor plate from side wall of carbody. Recently speedup and weight reduction of railway vehicle were achieved, interior noise can be higher because of rail noise and vibration transfer from bogie, which is transferred through traction link, floor of carbody, and joists to floor plate. The frequency of these structure borne noise is from tens to hundreds of Hz, and is considered difficult to reduce these low-frequency noise. Then lower vibration of side wall is noted by measuring carbody vibration, and suspended floor is proposed to reduce vibration transfer from carbody to floor plate. Two stationary vibration tests are conducted to by applying suspended floor to Shinkansen-type test vehicle. In the tests floor plate is suspended by band plate, wire, or plate from rack or skirt and rail noise is adopted by actuator, or by running on roller. Finally, vibration and interior noise reduction is achieved successfully.

This paper presents a structure-borne vibration analysis method of cylindrical structure using FEM model and Statistical Energy Analysis (SEA) method. The coefficient which contributes to reduce panel vibration using calculated Internal Loss Factor (ILF), Coupling Loss Factor (CLF) of SEA model was picked out. And we drafted the structure to which vibration of the panel can be reduced, and the effect was inspected by FEM analysis and FEM-SEA analysis. The drafted structure was contrived from the point of view to which input power is reduced, and it'll be expected to inspect the effect by experiment.

This paper presents a new active control method of sound radiated from a double-walled structure. The purpose of this study is to control of sound radiation power level using both of active noise control and active vibration control. First, modal coupling method is introduced which is required to model a vibro-acoustic coupling system. Then, optimal control laws of active noise control and active vibration control for minimizing the sound radiation power are derived in a vector form. Next, some numerical simulations are carried out to demonstrate the validity of the proposed method. As a result of the analysis, reduction of the sound power level is succeeded by feedforward control. Some numerical results show that active noise control is more effective than active vibration control for minimizing the sound power level. In addition, it is shown that by combination of the both control methods, improvement of a control performance is achieved. Furthermore, it is found that control effect rely on the relationship between placement of control sound sources and the disturbance location, while placement of control vibration source does not have significant impact on the control performance.

This paper describes a sound reduction method of the traveling-wave sound from a duct end using a piezoelectric sound absorbing panel. A side-branch type or expansion-chamber muffler has been used to reduce the radiated sound; however, these silencers require additional large space. In addition, to add damping to those mechanical silencers is not easy. In contrast, the sound absorbing panel requires a minimal space. Furthermore, the damping of the panel can be tuned using piezoelectric elements. Because the mechanical impedance of the panel should be decreased to absorb sound effectively and widely, a method that reduces the mechanical impedance using another piezoelectric element and a microphone is additionally proposed in this research. The governing equations were theoretically derived, and the effectiveness of the proposed method was verified through simulations and experiments.

In the design of the cabin such as a car and an agricultural machine, the construction machine, it is necessary to consider about the acoustic feature in the cabin, and to design it. However, we hear that it is possible only to the frequency range of approximately 0-300Hz by the analysis using FEM. On the other hand, the frequency range of 300-1000Hz, called ‘middle frequency range' is regarded as important about the design of the cabin, but the analytical method of this range is non-establishment. Therefore, in this study, we suggest modeling of cuboid space having sound absorption material and the analytical technique of the acoustic feature in consideration of the acoustic absorption effect with a wall and the seat. We suggested ‘impedance wall model’, ‘two medium model’ and ‘uniform absorptive sound field model’. Two medium model that were close analytical method, and the calculated value accorded with experimental value and was able to confirm the validity of the model. In addition, uniform absorptive sound field model that was approximate analytical method and accorded with an experiment with the calculated value in 1/3Octave band.

This paper describes an improvement method of the sound absorption effect for the piezoelectric sound absorbing panel. The piezoelectric sound absorbing panel has a high sound absorption coefficient at around the natural frequency of the fundamental vibration mode of the panel. However, the effective bandwidth is narrow because the sound absorption coefficient depends on the amplitude of the vibration of the panel. To solve this problem, we propose a resonance amplification method for the panel. The resonance of the panel is amplified by adding force to the panel using another piezoelectric elements in this method. The added force must be proportional to the sound pressure at the left-hand surface of the panel. Because this method requires a large value of an equivalent stiffness ratio of the piezoelectric element that enhances the equivalent stiffness ratio is also used in this method. The governing equations were theoretically derived, and the optimum values of the LR circuit were formulated. The effectiveness of this method was verified through simulations and experiments.

This paper describes an air spring cancellation method using a piezoelectric element and negative capacitor. Because the air space of the double-leaf wall functions as an air spring, the sound insulation effect is decreased at around natural frequencies of the double-leaf wall. In this study, the air spring is cancelled by the negative stiffness using piezoelectric elements and negative capacitor. The governing equations of the analytical model were formulated, and the optimum values of negative capacitance were derived. The effectiveness of the proposed method and theoretical analysis was verified through simulations and experiments.

Ball mills are the grinding equipment in the mineral and chemical processing industry. Many spherical objects called media are put into a mill with material, and the mill is rotated. In the mill, material is grounded by collision force due to contact between the material and the media. During operation, the mill vibrates and emits sound. The vibration and sound of mills contain information related to inside of the mill and are useful for operation control. If the relationship between the internal state and the information contained in vibration and sound is clarified, we are able to estimate the internal state of the mill. In this study, we develop simulation models for analysis of structure-borne sound from a ball mill during operation. At first, the motion of the balls in the mill reproduces by discrete element method. The simulation calculates collision force between the ball and the mill wall. Then, the collision force is applied as input force of vibration analysis by finite element method. The vibration response of mill wall is calculated. Finally, the radiated sound pressure is analyzed based on the result of the vibration analysis. The mill is divided into small element, and each element is regarded as a point source of sound. The simulations are performed under the different rotational speed condition. When the rotational speed increases, the velocity of collision with the mill wall also increases. As the result, the amplitude of mill wall vibration and sound pressure increase. Moreover, the sound pressure shows an influence of rotational speed more clearly than vibration displacement of mill wall.

Experimental modal analysis is widely used as a basic technology obtaining dynamic characteristic for mechanical systems design. In experimental modal analysis, input and output signals are measured. However, it is difficult to measure exiting force of mechanical structures because of a given boundary condition. Moreover, Operational Modal Analysis has been used on a field test, and the test structure is excited by the ambient force. When the input signals are unknown, the scaled mode shapes cannot be obtained. In this study, an estimation procedure for the scaling factors of normalized modal shapes is proposed. Furthermore, the real natural frequencies which excluded the effect of additional mass are identified by the mass change method.

This paper describes a new loudspeaker using a paraboloid and a point sound source. The purpose of this study is to generate linear sound space. Most of the sound wave from the focus of the paraboloid is reflected by the paraboloid surface, and the reflected sound wave becomes a plane wave. In this study, the reflected sound wave is regarded as an imaginary large piston that is located at the end of the paraboloid. The rest of the sound wave that is not reflected by the paraboloid becomes spherical wave. The acoustic filed is given as the sum of these acoustic fields. In this study, we propose a new point sound source device that has a flat frequency characteristic. The acoustic field is theoretically analyzed, and the effectiveness of the proposed method and theoretical analysis was verified through simulations and experiments.

Speech is produced by self-excited oscillation of vocal cords. In previous works, the vocal cords were modeled to perform by time history analysis of self-excited oscillation in various ways. However, eigenvalue analysis of coupled acoustic and vocal cords vibration has been not performed. In this paper, we propose a concentrated mass model to analyze a speech production and a self-excited oscillation in the vocal cords, this model can be applied to eigenvalue analysis. This model consists of mass points, connecting springs and dampers. And, we simulate a speech production by the concentrated mass model. Then, we conduct an experiment by using model of vocal organ. We confirm the validity of the concentrated mass model by comparing numerical results and measurement results. According to these result, it is concluded that proposed model is valid.

Ultrasonic bone conduction (UBC) can be perceived by a normal hearing subjects and a profoundly deaf person. The purpose of this research is to design the UBC speaker which is able to control the sound image localization in auditory sensation. The UBC speaker is constituted by the multilayer type piezoelectric actuator and the mounting device, which is produced experimentally. In the experiment, it is mounted on the mastoid or the front-back of head, and the distribution and angle of sound image localization were evaluated sensuality. The experimental results showed that the crosswise localization of UBC was more clear than the one's of air conducted sound. However, it is clear that the anteroposterior localization could not be control by the present investigation.

Global vibration reduction is difficult to achieve by local sensing. The difficulty comes from a poor observability of the structural modes, which occurs when the measurement point is near nodes of structural modes. Since modal shapes of the vibration velocity and its spatial gradients are different, the observability can be improved by sensing not only the velocity but also its gradients at a single measurement point. On the other hand, from the viewpoint of reducing the sound radiation rather than the structural vibration, the global vibration reduction does not necessarily lead to the global noise reduction, because radiation efficiencies of the structural modes are considerably different. A method to independently measure and control a cluster of the structural modes with high radiation efficiencies, cluster control, was investigated in earlier works, yet the difficulty in achieving global vibration reduction by local sensing is the same as the conventional vibration control. This study investigates cluster control with the error criterion being the vibration velocity as well as its gradients, and presents the control effects via numerical simulations. It was found that the cluster control including the vibration gradients facilitates the global suppression of vibration and noise.

Third party's conversation can easily ill influence on one's work efficiency. A sound masking method can be used for masking against the conversation sound on such a situation. This method is effective in open space such as office or living room. However, a noise level after masking inevitably be increased with conventional masking approach. In this paper, an approach aiming to decrease noise level after masking with active noise control is investigated. Since the virtual microphone method is used, no microphones are necessary in this approach. Recognition rates, the masking effectiveness, are evaluated with simulations and experiments at several points.

This paper describes the noise control for a moving evaluation point using neural networks by making the best use of its learning ability. Noise control is a technology which is effective on low-frequency noise. Based on the principle of superposition, a primary sound wave can be cancelled at an evaluation point by emitting a secondary opposite sound wave. To obtain good control performance, it is important to precisely identify the characteristics of all the sound paths. One of the most popular algorithms of noise control is filtered-x LMS algorithm. This algorithm can deliver a good result while all the sound paths do not change. However, the control system becomes uncontrollable while the evaluation point is moving. To solve the problem, the characteristics of all the paths are required to be identified at all time. In this paper, we applied neural networks with the learning ability to the noise control system to follow the time-varying paths and verified its control performance by numerical simulations. Then, dropout technique for the networks was also applied. Dropout is a technique that prevents the network from overfitting and that realizes better control performance. We concluded that applying dropout to noise control prevents the system from diverging.

Every year the City of Hiroshima holds the Peace Memorial Ceremony to console the souls of those who were lost due to the atomic bombing as well as pray for the realization of everlasting world peace. Since the ambient noise of this ceremony is very loud, these noise was tried to reduce using a passive method and Active Noise Control (ANC). There are some problems that audiences or TV crews cannot catch the meanings of presenter's messages such as the Prime Minister's, because of ambient noise. To reduce these noises, tents were prepared in the venue. There were also useful for protect people from the strong suns. The difference between the sounds near the loudest place in the park and those in the venue was measured to confirm the effectiveness of each countermeasure. The one of the loudest noise came from an opposite bank of the river. Though the noise was detected at the river side, it was not detected in the venue. As a result, the noise in the venue was reduced by 15 dB owing to each countermeasure. As most of the noise are speech, a 6-second young woman's voice was used as the noise source and reference signal in the ANC test of this study. Noise source includes the high frequency components up to 4000Hz. High-speed signal processing was required to reduce the noise that has high frequency components and changes its amplitudes rapidly. FPGA with a clock of 40MHz was selected for the fast signal processing. Filtered-x LMS algorithm was used in the ANC, and sampling frequency was 15 kHz and adaptive filter coefficients were set to 3000 tap. As the results of control, the noise was reduced by 10dB in 500Hz to 5000Hz.

In internal combustion engine development, the relationship between the improvement of engine performance and the reduction of engine noise is a balance; it is very difficult to achieve both objectives, however active noise control (ANC) presents an effective method to address this. With recent advances in digital signal processing technology, ANC, has been used in a number of products. In conventional ANC control, a loudspeaker is often used as an actuator, however the speaker's conversion efficiency is usually too low to control loud noise. In this study, we used a linear motor as the actuator, and examined the possibility of reducing the noise level via the air pressure change in the cabin. We studied the performance of the speaker and the linear motor in controlling a loud noise, and confirmed the effectiveness of the linear motor. It was shown that control of the air pressure change is effective.

Blind source separation is an approach for estimating source signals that uses only the mixed signal information observed at each sensor. Independent component analysis (ICA) is a powerful way to solve this problem if it is applied to instantaneous mixture in which travel time is not considered. If we want to solve the mixture in which travel time of source signals is considered, it has to be dealt in frequency domain. This way makes it more difficult to solve the problem in real time. Our approach deals the signals in time domain by neural networks. Neural networks have ability to predict by giving time series data as input. Therefore, we assume that it can predict the separated source from the time series data of mixed signals. As a result of simulation, we successfully separated the mixture of sine waves and single voices “a” which are spoken by male and female. Additionally, even if there are long time difference in traveling, we separated the mixture of sine waves.

In the case that unknown force excites the vibrating structure, the virtual exciting forces at any points are calculated from a number of measured accelerations on structure in the condition that actual vibration state is the same. In that the sound radiation power caused by the virtual exciting forces is set as an objective function, the noise reduction design is performed. In that time, the excitation sources of the virtual exciting forces are modeled and the parameters of excitation source model are identified from change in the measured accelerations in the case of structure change caused by added mass and stiffness. Identified parameters of the excitation source enable the structural optimization to reduce the radiated noise considering the change in the virtual exciting force caused by the structural change. For example, proposed method is applied to the optimal rib location enables to reduce noise in the case that the cantilever rectangular plate is excited by a lumped exciting force.

This paper examines the stiffness sensitivity analysis for reduction of the sound radiation from a mechanical structure. In order to decrease the radiated sound from the structure, vibration with respect to out-of-plane needs to be decreased. Therefore, the addition of bending stiffness is considered to decrease the out-of-plane vibration. This paper formulates the stiffness sensitivity analysis by using the strain measurement. The proposed method is applied to the mechanical structure: a rear frame of the motor cycle, as an example of the industrial product with reducing noise required. The response evaluation point is set on the frame structure that is a candidate location of noise radiation. The sensitivity analysis is applied in order to reduce the frequency response of the evaluation point within a certain frequency band. As a result, the reduction of the response is attained by adding the stiffening plate to a certain location on the frame. The location is effectively determined by analyzing the sensitivity with respect to stiffness and mass changes.

As the diesel engine used for the forklift and construction machineries is operated at the continuous heavy duty condition, it employs the gear train to drive the fuel injection pump and valve train. When the driving torque acting on the rotating shaft is decreased in the idling condition, separation of gear tooth and rattle noise are induced. Moreover, torsional vibration of crankshaft increases the impact vibration between the gear train. This gear train is commonly installed at the pulley side of the crankshaft and the gear casing is attached to an engine block to cover the gear train. Vibration level of this gear casing is often magnified due to the engine block vibration and consequently the engine noise is increased at the pulley side. The effects of changing the structure of gear casing and noise radiation from the gear casing are evaluated by use of the modal synthesis method which employs the vibratory characteristics of each structure and static deformation caused by the displacement of the connecting points. The rubber pasting on the gear casing is carried out to reduce engine noise. A modal damping ratio of coupled system after pasting rubber on the gear casing evaluated by use of modal analysis technique and its validity is confirmed by vibration experiment of a box model which imitates engine block and gear casing. Change of actual engine noise level by rubber pasting on gear casing is also discussed in detail.

This paper proposes excitation force identification method based on a physical model building. If reworking occurs after the assembly of the prototype in mechanical product, cost increases due to the retrofit countermeasures and development period extension. As conventional methods, the mount stiffness method and the matrix inversion method have been proposed. However, mount stiffness method calculates the mount transmission force. Therefore, if the development machine has structure change, preliminary evaluation does not apply. matrix inversion method can solve this problem. However, when the frequency response function contains a measurement error, there is problem that error at the time of invers matrix calculation is propagated to expand. Therefore, in order to avoid the inverse matrix calculation, we propose excitation force identification method based on a physical model construction of the vibration source. In this paper, it was investigated features of the inverse matrix method and physical model construction technique using the basic experiment and analysis. Study a result, the physical model building techniques showed that less than affected by the measurement error inverse matrix method.

This paper discusses a relation between subsystem energies and power flow in Statistical Energy Analysis (SEA) for vibration reduction. A test structure is coupling of several panel with 10 subsystems of flat steel plate. At first the optimization procedure is carried out to find a low-vibration structure by using analytical SEA (ASEA) in which coupling loss factors are theoretically evaluated. Then the relation between the subsystem energy levels and power flows from one subsystem to another in ASEA are discussed, and it is shown that the power flow is naturally transmitted from higher modal energy subsystem to lower. Next the optimized structure is tested to confirm low-vibration design by using FEM calculation. Also power flows in FEM-SEA of the optimized structure are evaluated to be compared with those in ASEA under high and low damping conditions. It is concluded that the power flows in FEM-SEA and Experimental SEA have the energy transmissions from subsystem with lower energy to another with high energy because of SEA subdivision way and having predominant modes as ordinary phenomenon.

The crankcase and oil pan in an internal combustion engine or the frame and panel in an automobiles are coupled systems of the flexible and rigid structure. In these systems, vibration of the flexible structure often becomes one of the major noise sources when the excitation force is applied to the rigid structure. Though the rigidity changes, mass addition and damping treatment are employed for noise control of these structures, FEM and modal analysis technique are not sufficient to carry out the effective low noise design. In this paper, new low noise design approach, Modal energy propagation method, is proposed based on the modal synthesis method and the vibration power flow between the eigen mode of the rigid and flexible structures. Reducing large vibration power flow between the eigen mode of each structure brings effective low noise design. This method is formulated based on the modal synthesis method which employs the vibratory characteristics of each structure and static deformation caused by the displacement of the connecting points. This method is applied to vibration control of the box and cover model and the availability of vibration power flow control approach are discussed.

The internal combustion engine encounters the cavitation erosion induced by piston slap. The impact vibration between the piston and cylinder liner generates the pressure fluctuation on the coolant side of the liner and leads to occur the cavitation in the case that dynamic pressure falls below its vapor pressure. Authors have already developed the analytical method to predict the liner vibration caused by the piston slap. In the previous paper, the acoustic characteristic of the water coolant passage of the actual diesel engine in vacuum condition was analyzed and compared with the measured result. In this paper, theoretical method to determine the coupled vibratory characteristics of structure and water acoustic field is developed. This method employs modal analysis technique and Boundary Element Method. Calculated results of vibro-acoustic characteristics of the multi-cylinder model are compared with the measured ones and the effect of the heavy fluid loading is examined.

An electric guitar is composed of a wooden body, a wooden neck, an electromagnetic pickup, 6 steel strings and other electric parts. The electric guitar changes string vibration into an electric signal with the electromagnetic pickup, and the sound is emitted through an amplifier. Usually, high density and high stiffness wood is used for a body material, to prevent vibration transmission from a string to a body. Then, string vibration sustain longer and the sound remains. Also, it is reported that the material of a body influences the quality of the sound. In previous study, vibration energy propagation of two test guitars composed of different body material are observed with experimental SEA, and a strong correlation of vibration propagation characteristics and sound pressure level is reported. To clarify the mechanism more in detail, correlation between frequency characteristics of string vibration and stiffness of edge is discussed in this report. To simplify the discussion, experimental set up only with string and several types of edge (with different stiffness) is built. As a result, correlation between edge vibration and string vibration is clarified by comparing fixed edge, and two elastic edges; string is more excited when vibration of an edge is transmitted and the edge itself less vibrates; frequency characteristics of edge influence on the frequency characteristics of the string; and vibration of string does not influence on frequency characteristics of the edge.

When the loading torque is small in the internal combustion engine and gear transmission, the gear tooth separation is caused by the fluctuating torque. One of the measures to reduce the gear impact noise is supplying the oil to the rattle part. In order to analyze the impact vibration behavior through the oil film, the numerical calculation using time integration technique is not easy task because the colliding stiffness and oil film damping are connected in series and the mass of the connecting point is zero. In this paper a new method to calculate the vibratory response of the dynamic system involving the gear backlash partially filled with oil film is offered and applied to vibration and noise radiation analysis of the internal combustion engine with a gear train system. The effect of the oil film in the backlash on the gear impact force is evaluated and moreover it is discussed the relationship between the gear backlash and engine noise changing with engine rotational speed.

The vibrations and noises occur from a drive system likely to increase when the driving speed of the Shinkansen improves. Particularly, the noise generated from gear case become high correlation in 1st meshing vibration occor from the pinion and gear. we measured vibrations and sounds of gear systems under running conditions in order to analysis the property of the systems. however, the separation of the sound source may be difficult because the rolling noise is included at the frequency that is almost the main frequency of gear noise(approximately,1kHz) .In this paper, We carried out bench test with fundamental modal analysis, Operating Deflection Shape analysis(ODS) and Beamforming analysis to acquire more detailed measured data on a noise generated from the gear systems. we found that the center of vibration and the sound radiation exist around bearing device or plate part of the bearing neighborhood.

An attempt to evaluate the impact noise due to rail joints was carried out by using the scale model tests. The derivation of law of similarity related to wheel/rail noise was made and actual phenomena can be estimated by the scale model tests. Through the measurement with an impact hammer, the vibratory characteristics of track and wheel are estimated in the scale model test with the law of similarity and they are compared with that of the actual track and wheel. It is found that overall trends are well-estimated. In the running test it is shown that the acoustic power of the impact noise is proportional to the power of 2.3 of wheel speed and it is possible that impact noise due to rail joints is simulated by the scale model test. To investigate a potential for impact noise reduction, the relation between impact noise and track parameters, e.g. a soft rail pad, is examined in the scale model test. It is indicated that soft rail pad leads to the reduction of the impact noise and sleeper vibration, though rail vibration is increased. The scale model test may also evaluate the properties associated with rolling noise. And in the vibration of the rail and sleeper the results obtained in the scale model test show a good agreement with those in the field test.

Helmholtz resonators are used in many industrial products as devices for reducing low-frequency noise. An advantage of the Helmholtz resonator is that the structure is simple and applicable to low-frequency noise for its size. Further, an important feature is that the development costs and product costs are relatively low in actual product development. The optimum combination of the natural frequency and modal damping ratio of a Helmholtz resonator is dependent on the characteristic of the noise source. It is selected so as to minimize the sound pressure levels when the noise is stationary. In the case of a transient noise problem, the natural frequency and modal damping ratio is tuned for maximizing the modal damping ratios of the system consisting of the main system and a Helmholtz resonator. Noise reduction effects of Helmholtz resonators are generally predicted by 3D acoustic analysis. Recently, the effects are estimated by CFD at higher sound pressure levels exceeding 100dB, because they are greatly affected by eddies generated in the neck portion of resonators. However, there is no suitable method to predict the noise reduction effects of Helmholtz resonators that engineers can use easily in the early stages of design. This paper describes a simple method for estimating the optimum value of modal damping ratios of the acoustic system having a Helmholtz resonator. Here, two-degrees-of-freedom models similar to the mass-spring-damper models used in the design of tuned mass dampers are used. In addition, the difference between the optimum condition of the maximization problem of modal damping ratios and the minimization problem of sound pressure levels are described.

One of the major noise problems in the heat exchangers for the thermal power and chemical plants is the acoustic resonance induced by vortex shedding of the flowing fluid. This phenomenon occurs when the vortex shedding frequency coincides with the natural frequency of the acoustic field in the heat exchanger and it sometimes leads to destroy the structure of the plants. Many researches elucidated that the vortex frequency is determined by Strouhal number and the direction of the acoustic resonance mode is perpendicular to the flowing fluid. Based on these research results, the baffle plate is inserted into the tube array to increase the natural frequency of the acoustic field of the heat exchanger. Recently it has reported that the acoustic resonance in the flowing direction at twice frequency of Strouhal number occurs and sometimes the acoustic resonance having the half or triple frequency of Strouhal number are observed. In this study, it is discussed the relation of three dimensional acoustic mode of the wind tunnel involving the tube array and the acoustic resonance induced by vortex shedding and furthermore the generation of higher and sub harmonic acoustic resonance are discussed.

We report the result of test that has given the acoustic excitation to the new guitar in the aging cell with using the Bach's cello suites. The sound quality effect of playing the guitar for five years is the same as one of the four weeks aging test with the high load. However, the too much aging gives the new guitar the adverse effects. In this time, we were able to have the good balance results with the light load aging. But there were few effects in the upper position sounds of the guitar. The sound range of the cello is not enough to the acoustic excitation of high frequency zone. So, we will try soon the aging test with playing the violin pieces.

Cymbals are thin domed plates used as percussion instruments. When cymbals are stuck, they vibrate and radiate sound. Cymbals are made through spin forming, hammering, and lathing. The sound radiated from a cymbal depends on its vibration characteristics that are determined by the shape and dimension. The hammering produces plastic deformation on the cymbal's surface, generating residual stresses throughout it. Although the vibration characteristics are changed by the hammering to adjust cymbal sound, the effect of the hammering on the cymbal sound is not clear. In this paper, we reveal the effect of the hammering on the vibration and the sound radiation characteristics. The stress distribution within the cymbal produced by hammering is reproduced by thermal stress analysis and the change in natural frequency of the modes are calculated by the vibration analysis with the stress distribution. The change (i.e., increase or decrease) in natural frequency for each mode is explained by the stress and modal strain energy distributions.

Electric guitars are designed to generate sound of strings' vibration by amplify electrified signals with electromagnetic pick-ups. Resonance of body is not considered, so usually bodies are made of solid woods and raw sound radiation is very small. Advantage of electric guitars are that tone and volume are easily modified with various effectors. Thus, dominant factors of the sound is electric, but still mechanical structure of the guitar influence on the tones. In previous researches, there are some reports those mentioned about influence of woods' characteristics, but there are few reports in terms of vibration propagation analysis. On the other hand, authors aim on reduction of noise and vibration with devices be inspired of mechanism of instruments. In this study, relation between vibration characteristics and coupling methods of guitar is discussed with statistical energy analysis, so called SEA. First, influence of strings on vibration propagation characteristics is discussed with experimental SEA. Then, relation between vibration propagation and two coupling methods is discussed; number of bolts to fasten neck and body is changed. Finally correlation between sound tone, vibration propagation characteristics, and two coupling methods are reported. still In this study, focus on vibration energy propagation characteristics of structure. Therefore, the picking for which reproducibility has been secured was adopted.

This paper describes vibration analysis methods of a multi-dimensional coupled vibration system. In particular, the vibration analysis of the structural-acoustic coupling vibration system and acoustic-acoustic coupling system is described in this paper. The structural-acoustic coupling vibration system was analyzed using the equivalent replacement of the displacement excitation into the equivalent force excitation and a fixed boundary. The acoustic-acoustic coupling system was analyzed by two methods: one method installed a significantly light and flexible plate into the interfacial boundary, and the other method used an acoustic field whose interfacial face was opened for the smaller acoustic field. Because Gibbs phenomena were observed near the displacement boundaries using the proposed methods, the coordinate transformation that reduces the Gibbs phenomena was also described in this paper. The effectiveness of the proposed method was verified through the comparison of simulation results using the proposed method and exact solution.

This paper proposes a health monitoring system for detecting a hole opened on a pipe based on laser plasma acoustic excitation and acoustic measurement. In this system, the acoustic excitation is applied to the pipe by the laser-induced plasma in the air, which is generated by a high-power Nd: YAG pulse laser. Non-contact acoustic impulse excitation can be realized by laser-induced plasma. A microphone is used for measuring the time response of acoustic pressure. In this study, the detection of the hole on the pipe is focused. The time response of acoustic pressure changes due to reflection of acoustic wave caused at the hole opened on the pipe. The position of the hole is identified by applying continuous wavelet transform to time response of with/without the hole.

Since the 1950s, techniques for reciprocating compressor monitoring have been developed. However, they cannot locate damage points in advance and have difficulty in assessing the degree of damage. The purpose of this study is to establish a new monitoring technique to detect the state of sliding portion and connecting portion, where it is known that some failure often occurs. In this paper, we examined the feasibility of estimation for the state in which the support rigidity of the sliding portion using the vibration characteristics in the experiment for a small experimental equipment. To estimate the state of sliding portion, we employ two kinds of material, carbon and molybdenum steel as the ring bush of the ground support. We determine the model parameters using both the natural frequencies obtained from the experimental and the eigenvalue analysis based on the inverse problem. Namely, we were assessed difference of the natural vibration characteristics comparison of the mathematical model with six and eleven degrees of freedom. As a result, it is found that we can estimate the characteristics of the sliding portion by focusing on the natural vibration characteristics. In particular, it showed the possibility of estimating the condition of sliding portion using mathematical model with eleven degrees of freedom.

Recently, we have faced on the problem such as increasing elderly people who have occurred accidents including lonely dead and falling and so on at their houses. To deal with this problem, many researchers and companies are proposing and releasing systems monitored by sensors for keeping them safety. However, conventional systems using sensors including cameras and microphones give little privacy. Thus we proposed the falling discrimination using sound information for watching elderly people. Proposed system expects the falling discriminations using acoustic features extracted from sound. For discrimination accurately, we focused on Spectrum gravity between subjects/things and floorings. The feature characterized and modeled as Spectrum ratio of delta power as dynamic parameter. Finally, experiments of two-class discriminations using feature parameters achieved to 96.83 % with dataset of unspecific conditions.

A generation method of undulatory motion of an aquatic flexible plate was addressed to improve the efficiency of an aquatic propulsion mechanism by suppression of a reflection wave on a trailing edge. Firstly, non-reflection impedance of a flexible plate was derived by using a matrix-based wave approach, and then control forces for trailing edge of a plate was derived by the impedance. Secondly, obtained non-reflection impedance was translated into the relationship of the displacements between leading edge and trailing edge, to generate a pure traveling wave by four linear actuators. In this paper, in order to improve the thrust, the channel to surround the elastic plate was introduced. Further we conducted PIV measurements to visualize the flow around the flexible plate. Experimental results show that a channel reduces the phase velocity of an aquatic flexible plate. The results indicated that the added mass effect was induced by the channel. Finally the method was applied to an experimental apparatus. The results showed thrust improvement by the channel.

The proposed method which estimate the responses of vibration without using exiting forces is found useful for the practical development in industries, even if numbers of the measuring points and used modes are reduced, and Guyan’s static reduction is applied for the beam model. The responses of vibration are usually calculated by modal parameters and exiting forces, however force estimations spend the long time and manpower. The proposed method is able to calculate the responses after the modification of a structure by (a) prototype vibrations of designated points on running conditions, (b) modal parameters of the structure before modification and (c) stiffness and mass matrix difference of modification area before and after modification. These data are usually already available for noise and vibration development, so that the proposed method does not need additional man power.

Recently, vehicle components like gasoline direct injectors are developed based on 1 dimension simulator which can be applied to the early design stage of product development. Further, the vehicle components are more complex structures to achieve high performance, and the impact behavior is more complex. Therefore, in order to estimate performance of components, rapid and high-precision method to calculate impact behavior is required on early design stage. In this paper, we show the method, which provides the impact simulation method by using eigenvectors to clarify impact phenomena. We applied this method to impact phenomena for direct gasoline engine injectors. This method can reduce elapsed time by approximately 84 percent than explicit method of full matrix and clarify predominant vibration mode in impact states.