In recent years, with rising concern about environmental issues, noise reduction in motors has become a stringent requirement. There are three kinds of acoustic noise in a motor: ventilation noise, machine noise and electromagnetic noise. This paper focuses on ventilation noise. This paper proposes a new method for designing induction motor fans. The purpose of the new design is not only to reduce the blade passing frequency (BPF) noise but also to minimize the unbalanced force in rotation. Application of the newly designed fan contributes to ventilation noise reduction of induction motors.

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Increasing interest in environmental matters, a quiet motor are drastically demanded lately. Among of acoustic noise of the motor, electromagnetic acoustic noise is jarring and is studied recently. Electromagnetic acoustic noise is strongly affected by (1) increase of magnetic density by reduction of motor size and (2) decrease of stiffness by right weight. In order to reduce electromagnetic acoustic noise, it is necessary to design the motor, of which natural frequencies of does not coincide with electromagnetic force frequencies. In order to avoid the resonance of the natural frequencies of the core and the electromagnetic force frequencies at designing phase, machine designer has to accurately predict these frequencies. In order to reduce the electromagnetic acoustic noise, this paper studies the following things, which are not clarified in previous research. Simulation method of the natural frequency in laminated steel sheet stator core

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An air conditioning equipment is usually set in a rail vehicle in order to keep comfort. However the noise is offensive to the ear especially when the rail vehicle is in a stop. Then the noise reduction is very important from the point of view of keeping the car room comfortable and is one of the distinguished techniques. This paper describes characteristics of flow noise generated from the duct with some holes. Both the acoustic experiment and the flow experiment were carried out in various parameters such as the flow velocity, the absorbing ability and the hole area by use of the straight duct. As a result, it was clarified that the noise reduction effect of the absorbing treatment was a little when the noise source was made only by the flow and is much when the fan noise is greater than the flow noise. Moreover the effect of the flow on the noise reduction effect of the absorbing treatment could not observed in case of the velocity being less than 30m/s.

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This paper describes the thermoplastics reactive type sound absorber. We can form one structure absorber with holes by injection expanded molding. The injected long glass fiber reinforced polypropylene can expand twice or more by spring back effect. The thickness of surface layer, which does not expand, and the inner porous core are about 0.5 and about 8mm, respectively. By opening holes in one side of surface layer, resonance type sound absorber is made. By changing radius or interval of holes, absorption frequency can be controlled freely. Resonant frequency must be revised by air flow resistance of expansion layer.

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The arrangement of the dynamic vibration absorber that decrease the radiation sound from the thin plate was studied. In previous work, we proposed the algorithm that decided the optimum arrangement of the dynamic vibration absorber. However, it is not necessarily practical because it takes time to decide the arrangement. This study shows that the vibration can be effectively decreased by the dynamic vibration absorber arranging periodically at intervals below 1/2 wavelength of the bending wave of the panel. Moreover, it was clarified that a triangular arrangement was more effective than a square arrangement.

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The dynamic vibration absorber using the free-free beam where midpoint is attached to a panel structure, which is vibrated at constant amplitude and constant frequency, can reduce the sound radiation from the panel at the anti-resonance frequency. This study explains about the method to estimate the equivalent mass that is needed to estimate the noise-reduction level at the anti-resonance frequency. And this study proposes that the free-free beam where both ends are zigzag shapes has several anti-resonance modes of multi-degree-of-freedom system. By using the proposed method for the proposed absorber, the anti-resonance frequency and the equivalent mass can be designed size-by-size.

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In the flux-path control magnetic suspension system, the force acting on the floator is controlled by moving a control plates made of ferromagnetic material, which is located between the permanent magnet and the floator. In this paper, the three-dimensional attractive forces acting on the floator were measured with a manufactured load cell. In addition, stable three-dimensional positioning was achieved by applying PD control. Several dynamic characteristics were measured in each direction

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As elevator rope has little damping, it may be excited greatly at the resonance frequency due to earthquakes. It is not easy to install a damping device to the rope because the elevator moves up and down. In this paper, a new damping device which consists of a spring and a magnet is proposed. Furthermore, the relation between modal analysis and transfer matrix analysis was theoretically explained by Lorrain development, and the utility of latter one for the model in this paper was described. Then, the effect of the proposed device was verified by using impedance.

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Recently, riding quality becomes an important item for elevator system. Many studies on vibration suppression of elevator have been conducted. In this paper, vertical vibration suppression by controlling the torque of the elevator traction machine motor is discussed. Additionally, the effects of the switching of linear controllers designed by H-infinity control theory according to the position of the elevator are also examined because the transfer characteristic from motor torque to car acceleration depends on the rope length from the car to the main sheave. The simulation result shows that the car vertical vibration is efficiently suppressed by adopting this method.

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A wave absorption control of beam near fixed boundary by finite difference (FD) approach is presented. The FD equation of motion of the node under the influence of the boundary condition is compensated to be the same as that of the inner node free from the boundary condition by control. The control strategy consists of a real-time convolution integral of the measured displacement and the transfer function that is obtained by the inverse Laplace transformation of the frequency domain control transfer function. We confirmed the effectiveness of the wave controller by the time domain simulation.

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This paper considers an active wave control of a rectangular panel. It is the purpose of this paper to expand the active wave control method of a one-dimensional structure for a two-dimensional structure case and to clarify fundamental properties of the control system. Firstly, a transfer matrix method for a rectangular panel is introduced to describe the wave dynamics of the structure. This is followed by the derivation of feedforward control laws for absorbing reflected waves or eliminating transmitted waves. Then, from a viewpoint of numerical analyses, basic properties of the proposed method are verified. It is found that the reflected wave absorbing control enables the inactivation of all vibration modes, and the transmitted wave eliminating control enables the generation of an almost vibration-free state.

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We propose a design method of a nonlinear anti-windup controller for discrete-time systems subject to l2 disturbances. The proposed controller is composed of a gain-scheduled feedback control law and a standard observer. The gain-scheduled control law has a structure that a high-gain control law and a low-gain control law are interpolated by a single scheduling parameter. The scheduling parameter is computed on-line by solving a convex optimization problem based on the information of the state variables estimated by the observer. We show that, by using the proposed control law, both a large region of attraction and high disturbance attenuation performance can be achieved.

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Although neural network controllers have high performance of controllability, it is difficult to guarantee stability due to their nonlinearity and complexity. We showed a design method of structures of neural network controllers for active control of vibration systems considering not only controllability but also stability. The structure of neural networks was layered and designed to identify linear single-degree-of-freedom (SDOF) systems for vibration control on the basis of the equation form of the systems with linear acceleration method which is one of numerical integration methods. The performance of the controller was compared with that of a turned PID controller.

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As a typical control subject, inverted pendulum systems have been used to investigate effectiveness and feature of control methods. In this report, we applied a subspace control and swing up control based on Jacobian elliptic functions to swing up and stabilize a serial double inverted pendulum system. For swinging up pendulum, energy control is a most popular method now. On the other hand, we propose to cause a nonlinear resonance in order to swing up pendulums easily. The effectiveness of new swing up technique is verified by numerical simulation.

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Generally, it is difficult to stabilize and swing up multiple inverted pendulums simultaneously, because control inputs to stabilize pendulums and to swing-up a pendulum interfere with each other. In this report, the subspace control and the swing up method using nonlinear resonance are applied to a triple inverted pendulum system. It is possible to avoid the interference between two kinds of control inputs by using these methods. Furthermore, the optimal condition to switch the control inputs from swinging up step to stabilizing step is proposed and the effectiveness of the proposed methods is verified by numerical simulation.

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The invert pendulum is often used to confirm the control theory and a new control design, because it is unstable system and an experiment on it is easy. This paper has a discussion about a swinging-up problem of the inverted pendulum. While usually an inverted pendulum is swung up by the horizontal movement of a cart, we propose a new swing-up method by both a horizontal and vertical movements of a cart. The movement of a cart is defined to increase energy of a pendulum. With the proposed method, a time for swing- up is shortened. An effectiveness of the proposed method is confirmed though the experiments. Since the proposed swinging-up control does not use system parameters for example a mass and a length of pendulum, the proposed control has robustness against parameter fluctuation.

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The responses of the controlled inverted pendulum to vertical oscillation are discussed. The authors investigate the responses of the inverted pendulum, which is stabilized by the optimal controller, to the vertical vibrations. With theoretical analysis, numerical simulations and experiments using the large scale vibration exciter, the stability to the vertical vibration is examined. The results show the system dynamics is governed by the Mathieu equation, thus the frequency response reaches its peak when the frequency of the forced vibration is twice as high as the natural frequency of the controlled inverted pendulum system.

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Linear equation of motion consists of mass, stiffness and viscosity, and is deduced from the energy law. Functions of mass and stiffness are clearly explained by the law of conservation of mechanical energy. But usually, it is said that viscosity can not be explained by the energy law. In this paper first, relation between viscosity and potential energy is made evident. Second, generation mechanism of viscosity is made clear from the standpoint of nuclear physics.It is newly introduced that the inflect point of Lennard -Jones potential decides the boundary between the elastic and the viscous regions. Third, the reason is presented why viscosity dissipates mechanical energy by changing it to thermal energy. Forth, it is made clear how viscosity yields the resistance force proportional to given velocity.

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A coupled inverted pendula model of competition and cooperation is proposed to obtain a purely mechanical expression of the dynamics of Lotka-Volterra competition models. The numerical result shows that the proposed model can describe the desired dynamics, that the equilibrium points of the model can represent draw, victory or defeat, and defeat togethor, and that there are initial conditions near all the equilibrium states of the model. It seems that the obtained behavior of the model contains competitive dynamics of can be compared with martial arts trick.

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This paper illustrates fundamental structures in Lagrangian and Hamiltonian dynamical systems. It is shown that the canonical symplectic structure can be naturally defined in the momentum phase space, namely, the cotangent bundle of a configuration manifold and also that a Hamiltonian system can be defined in the context of the canonical symplectic structure. As its dual structure, it is demonstrated that a symplectic structure called the Lagrangian two form on the velocity phase space, i.e., the tangent bundle can be induced from the canonical symplectic structure on the momentum phase space by the Legendre transformation for the case in which a given Lagrangian is regular. Then, it is shown that a regular Lagrangian system can be defined in the context of the induced symplectic structure.

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It is well known that the vibration and the noise of agricultural machinery during running on a road is strongly influenced by the lug form. In this paper, natural frequencies and mode shapes of a non-rotating Agricultural Tire are assesed by experimental modal analysis method for two boundary conditions: not in ground contact and in ground contact. These experimental results are compared with the flexible ring model which depicts the tire as a ring supported on an elastic foundation. The parameters of the model are identified from the measured natural frequencies by the optimization method. The influence of boundary conditions on the parameters is investigated. Further, the effects of several factors on the parameters are discussed.

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Bolted joints are widely used in mechanical structures. When dynamic characteristics of a cantilever beam are considered, the fixed end is assumed as an ideal fixation condition. In the actual case, the fixed end is often realized using bolted joints and the boundary condition isn't always an ideal fixation condition. In this study, dynamic characteristics of a cantilever beam with various boundary conditions are experimentally investigated. The normal condition is a bolted joint with adequate torque and locations of bolts. Other conditions are bolts joints with weak torque and adequate locations of bolts, and adequate torque and inadequate locations of bolts. And the natural frequencies and damping ratios are determined from the resonance curves. As a result, it is recognized that the natural frequencies and damping ratios are significantly changed in the case of an inadequate torque and locations of bolts and the higher harmonics of vibration can be observed at the condition. It is considered that the length of a cantilever beam changes during one period of vibration so that the nonlinear characteristics are appeared. These results can be applied to the diagnosis of machines and structures.

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The separation of mixture consisting of copper and polyvinylchloride (PVC) was studied experimentally and analytically. The separator consists of a vibratory feeder equipped with two plate electrodes, and they can be inclined about two axes with respect to the horizontal plane. The principle behind the separation technique is based on the difference in Coulomb force acting on the particles. The separation tests were performed with chopped waste electric cables. The effect of electric field strength and triboelectric charging time on separation efficiency was investigated. It is shown that it is possible to obtain high purity and recovery.

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This paper deals with the analytical reproduction of the squeal phenomena generated in a certain type of bicycle disc brake unit. It was made clear that the squeal was in-plane vibration in the direction of a disc surface with frequency about 1000Hz caused by frictional characteristics with negative slope with respect to the relative velocity according to the numerical analysis of the both in-plane and out-of-plane vibrations, and was generated in the vibration system including the brake unit and spokes. The analytical model of the bicycle disc brake system was set up. The resulting frequency of the squeal and the unstable vibration modes of spokes and rotor agreed well with the experimental ones.

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Recently, the brake noise reduction is one of the most important environmental issues for railway passenger transportation. In this study, a friction-induced self-excited oscillation and accompanying noise of a tread brake system were experimentally investigated by using a brake dynamometer. The dynamic behavior of both composition brake shoe and brake shoe head were measured by using accelerometer, and then a negative damping ratio of the system was evaluated. In order to suppress brake squeal successfully, a passive damping augmentation device is required. According to the identified negative damping ratio of the brake system, a simple oil damper attachment for the system was proposed. The experimental brake test results demonstrated the brake squeal suppression capability of the proposed damper.

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This paper focuses on a design solution for contact optimization that reduces the brake squeal noise. A front disk brake system is used as an example for the investigation. In the former, the finite element method is used to analyze the relationship between contact location of pads and squeal index that means a real part of complex eigenvalue. Parametric studies are performed to find out the better friction surface shape. In the latter, a new approach is proposed. It takes distibuted spring model as contact stiffness between components, and then calculates sensitivity of each spring. The proposed method is applied to an automobile disk brake and shows the practical use.

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This study presents experimental and analytical results about the influence of pad chamfering on squeal vibration in the disk-pad-caliper system, which is modeled after an actual disk brake. Chamfering of the pad on the leading edge decreases the sound pressure level of squeal. On the other hand, chamfering of the pad on the trailing edge has no relation to the squeal vibration. To clarify the influence of chamfering on squeal, we analyzed the disk-pad-caliper system as a surface contact analysis model, which combined the disk with pad-caliper by distributed springs.

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Recently, the vibro-acoustic systems are often analyzed in strongly coupled conditions in order to investigate the structure modification for the noise reduction. Therefore, the precision for the vibro-acoustic coupled analysis need to be assured. This study predicts the dynamic properties of a vibro-acoustic system by FEM analysis, and verifies the estimated properties by conducting the experiment. A simple vibro-acoustic system imitating the car cabin is set up, and experimental modal analysis is conducted by the impact hammer excitation. The experimentally acquired dynamic properties are compared with the numerical analysis by FEM.

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This paper presents generalized design method of a spatial filter for suppressing modal observation spill over. Using singular value decomposition of a modal matrix of the selected modes which is to be suppressed, filter design and optimal sensor placement can be simultaneously computed. Then the measures of modal observability is introduced as criteria for designing the optimal filter in a engineering sense. The validity of the method is investigated by experimental application to a cantilever beam.

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The low vibration and noise design of air-conditioners becomes the most important issue. In this paper, the estimation method of structure-borne sound from fan is presented. The experiment that axially excited the fan and the measurement of the resin characteristics that used the test pieces were carried out. Moreover, the numerical analysis was carried out by using the material properties, and the high accuracy result was obtained. As a result,the vibration noise radiated from the fan by the excitation power generated by the motor in the proposed analytical flow was able to predict.

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Friction between two relatively sliding surfaces possibly excites the structure with unstable vibration response that emits squeal noise. Many methods have been developed to predict squeal noise using theoretical models of structures. In this paper the authors propose an idea to predict the possibility of squeal noise occurrence in a real structure with friction by means of experimental spatial matrix identification. Using spatial matrices that derived from experimental modal data, mode coupling that causes instability of the structure can be predicted. This method can make it possible to predict the incident of squeal noise within the practically realistic range of friction coefficient and contact stiffness. The method is presented with showing an experimental verification study using a simple L shape frame.

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The authors are developing a vibration simulator, which consists of field-portable exciters (actuators) and data processing software, to estimate vertical vibration and riding quality of railway vehicles. One of the main characteristics of the vibration simulator is that the acceleration power spectral density (PSD) at arbitrary point on the carbody while running is synthesized numerically from measured data obtained when each axle box or each wheelset is excited individually. This report focuses upon the data processing technique of the simulator. A series of excitation tests for a commuter vehicle was carried out to confirm the basic concept to synthesize (estimate) the PSD by using the rolling stock testing plant as exciters. Several excitation methodologies and data processing formulae are compared among each other in this report. It is shown that the estimated PSDs well agree with actual PSDs. It is found out that the estimation gives high accurate results when each wheelset is excited individually and acceleration values at excited axle boxes are used in estimation analysis.

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Bending vibration characteristics of railway vehicles have been investigated in general under excitation tests, in which a carbody was directly excited by a shaker. It is however very difficult with their results to evaluate the ride comfort of passengers under a condition that the vehicle runs on a certain track. The authors are therefore developing a "vertical vibration simulator" for railway vehicles. The simulator consists of a excitation system equipped with linear actuators, the elastic supporting device installed between wheels and rails, and analytical techniques to estimate the power spectral density (PSD) and the ride comfort level (L_T) which feature the ride comfort. In this paper, we describe the excitation tests performed using an actual commuter car and the estimated PSD and L_T are compared with what substantially measured under the running conditions.

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Recently, buildings tend to be higher-rise and to have larger capacity, and then vibration of an elevator car is likely to be larger. The suppression of vibration is needed and active control system has been developed for the ride comfort. For the vibration control, the dynamic characteristics of the elevator car need to be determined under the operating condition. In this study, the frequency response functions (FRFs) are measured during the operation by using actuators. The dynamic characteristics of the elevator car are modeled by a rigid body that is supported by springs. The stiffness parameters are estimated so as to minimize the errors of FRFs between the model and the actual car.

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The method of conventional experimental modal analysis in our laboratory is difficult to measure the vibrational characteristic of rotary structure which was under operation. So, the final purpose is to investigate the vibrational characteristic which was under operation. For that, we analyzed the experimental mode by using strain gauge, because the acceleration pickup that had been used so far wasn't able to be used which was under operation. And we investigated the vibrational characteristic by using the acceleration pickup and the calculation by computer before operating experiment. Then, we compared each other and examined the correspondence of the result used strain gauge. And we calculated strain modal shape under operating.

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The force acting on a machine or a structure must be identified when they are designed or in case of condition monitoring and diagnosis. One of the force identification methods is based on the frequency response function. The method is very useful although it requires the information of location of force acting. In this study, the identification method is improved such as to apply the case with no information of location of force. The method is numerically checked and it was shown that the method was useful in the case with and without noise in the measured data. Moreover it is checked by experiment.

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Continuous operation of rotating machinery with a rotor crack is a risk condition since the rotor crack grows rapidly and may fail causing a catastrophic accident. This paper investigates the estimation of both the depth and position of the rotor crack by utilizing the natural frequency of the rotor system with a breathing crack. First, by using the finite element method, the dynamic responses of a cracked rotor system under applying periodical external excitation are investigated. The natural frequency of the case with breathing crack is calculated by using that of the case with open crack. From the obtained natural frequency, the occurrence frequency of the sub-resonance due to crack is calculated for various values of depth and position of the crack. The estimation method of both the depth and position of the breathing crack is proposed, and it is validated by the numerical simulation.

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A modal-based, simplified and practical algorithm to evaluate the local flexibility of structures is presented in this paper. Local flexibility indices for translational or rotational flexibility are adopted as damage metrics, and their approximate calculation scheme is proposed. Using the proposed algorithm, one can detect the extent of the local damages by using only the first few modes, whereas such damages cannot be detected by using the global feature such as natural frequencies. Furthermore, because the proposed damage index is evaluated from dynamically-identified mode shapes without calculating mass-normalization constant, this methodology can be realized in a decentralized form by installing a couple of sensors per one location of interest, not deploying many sensors throughout the structure. Experiments using a laboratory-scale test structure are carried out to show the potential advantage of the proposed algorithm when embedded in a wireless sensor network environment.

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In this paper, a method to identify the geometrical shape and the location of the defect embedded in a concrete structure by processing the thermal image of the structural surface is presented. In the proposed method, a layer-by-layer inverse analysis using an inverse filter based on 2D Fourier transform is carried out to obtain the sharper image of the defect as well as the depth of the damaged layer. The effectiveness of the proposed technique has been examined both numerically and experimentally.

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In this paper, we propose a design method of the fault detector which detects and isolates the faults of the injection unit. The injection unit has the reaction force sensor, and it is controlled by a speed feedback controller. We construct a residual generator by using an disturbance observer which estimates the reaction force, and we give a fault detection system that utilizes the residual signals. The properties of the transfer functions from the equivalent fault disturbance to the residual signals are analyzed, and the frequency characteristics of the speed control system and that of the reaction force are utilized. The fault detectability is shown by constructing the fault detector. Usefulness of our method is verified by the simulation with the actual parameter values of the injection unit.

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This paper provides a new fault detection algorithm for improving reliability of smart structures. The proposed method is based on a subspace state space system identification (4SID) method. A recursive 4SID fault detection algorithm has been developed by using both residual signals and estimated system parameters. It is shown by the hardware experiment on a flexible smart beam that the proposed algorithm is highly effective for detecting abrupt changes in the dynamic response of the closed-loop system by using the measured displacement data.

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Fault detection methods based on empirical models such as principal component analysis (PCA) or support vector machines (SVM) are compared. As an example of realistic plants, absorption chiller system is chosen for comparisons. Several datasets whose distribution show different degrees of nonlinearity are generated based on an empirical model which describes heat exchanger efficiency. Sample numbers for model training is crucial on fault detection ability of models, especially for SVM. Nonlinear distribution of observed plant data deteriorates fault detection sensitivity of linear PCA model, whereas it does not affect SVM model.

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This paper describes a preliminary study of an activity monitoring system for a residential house based on Bayesian networks. For the demonstrative purpose, a proof-of-concept system using vibration measurement has been proposed, in which specific physical features of the vibration that may indicate either daily activities of residents or other disturbances such as traffic-induced vibration are extracted from the collected data. Vibration data is classified into two groups based on these features, and the attribution degree was defined based on the support vector machines associated with the extracted data classes. A Bayesian Network is designed as the data model that represents the relevance of the data classes to external variables such as time and in/out status status. Finally an abnormality index has been proposed and investigated based on the likelihood evaluated on the trained Bayesian network.

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Detection and monitoring of machinery component deterioration by checking the debris in lubricating oil are desired for early prediction of the failure. For hybrid bearings with silicon nitride rolling elements, however, it is difficult to detect the wear debris because the particles are non-magnetic and non-metallic ceramics. This paper proposes a mechanical detection system, which can sense the size and amount of such debris by using a capacitance detector, and reports some experimental results using a sensing apparatus consists of two electrode plates and a linear actuator.

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In this paper, we developed a tool holder with torque sensing function in it by using a magnet coupling with magnetoresistance sensors. Cutting torque cases a shift between two signals from two magnetoresistance sensors. We can estimate torque by estimating a shift between two signals from two sensors. Finally we confirmed that a developed tool holder with sensing function showed almost same accuracy as a torque sensor provided by Kistler.

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The on-line performance monitoring of a shell-and-tube type heat exchanger using water and steam, which is one of the key components of distributed energy supply systems, has been developed on the basis of a theoretical model. By using a steady-state model of the heat exchanger, this performance monitoring first estimates output process variables and heat exchange performance of the heat exchanger in response to the variation in measured input process variables. These estimated values are then compared with the measured ones for the on-line performance monitoring. Its effectiveness has been confirmed by the demonstration experiments conducted not only in the steady and transient states but also under the condition of air accumulation in the shell as one of the common failures of this type of heat exchanger. The results confirm the sufficiency of the estimation accuracy of the output process variables and heat exchange performance in a wider operating range and the detection capability of the deterioration of the heat exchange performance due to the air accumulation in a short period.

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A non-intrusive vibration measurement system using an ultrasonic sensor is developed. This system can measure pump shaft vibration from outside of pump casing. However, this system can measure only the vibration of the ultrasonic propagation direction. We are developing a method to measure the vibration of a perpendicular direction of the propagation direction by measuring the level change of the echo. This paper describes the result of test to measure the vibration of the tube which simulated a heat exchanger tube.

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Damping of pressure pulsations in piping systems excited by centrifugal compressors or blowers at blade-passing frequency dominates acoustic resonant characteristics. In this study, the relation between the resistance coefficient of the compressor and the operating point was investigated experimentally. As a result, the resistance coefficient of the compressor depends on the Reynolds number defined by the equivalent velocity of the pulsating flow. It is shown that the pressure pulsations in piping systems can be evaluated by one-dimensional wave model taking into account the damping characteristics of the compressor.

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Maintaining of the integrity of reactor pressure vessels and reactor internals in BWR is one of the focal points to secure stable and efficient plant operation. Pressure pulsation associated with reactor recirculation (PLR) pump impellor motion has potential risk of acoustical-induced-vibration, resulting in material fatigue failure. Experiments were performed to improve and validate the evaluation methods. As a result of experiment, the acoustic mode shapes and frequency response showed the good agreement with those of numerical simulation. The simulation confirmed to predict the mode shapes, frequency response and pressure pulsation.

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This paper presents the model test results of self-excited vibration of the air supply valve for the ring flower gate in the water release pipe system of dam. The water release pipe system has the main gate and the sub-gate. The sub-gate surely has air valve for inhalation of air. The intense self-excited vibration was occurred in the water release pipe system under practical use. The intense vibration occurred when the air valve was closed, while water was accumulated in the pipe system. Although it is thought that the water hammer generated in the upstream participated in this problem, the main reason is not clarified. In this study, the self excited vibration related to the actual problem was revealed, using the model of the water release pipe system and the air valve.

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