The improvement of the comfort of vehicles becomes an important problem in the automobile design in recent years. A whole-body vibration that relates to ride comfort, tiredness and so on is one of the factors that relates to the comfort of vehicles. The human body receives the vibration from a seat finally. The automotive seat is consisted mainly 3 parts, a frame, a urethane cushion and a fabric. At the planning phase, the frame of the seat is considered about the safety. A problem of ride comfort was addressed by the urethane. The characteristics of vibration of the frame have not been focused on. It is necessary to understand the characteristics of vibration of the frame. Therefore, the purpose of this paper is to understand the characteristics of vibration of human body-seat coupled system. Understanding the characteristics of the automotive seat, we consider influences of vibration of the frame of the seat on a human.

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We quantified the sense of ride comfort Mr. Mitsumoto has, who has been a car journalist for a long time, with a new evaluating method called sensitive response MAP using the physiological index (Aortic Pulse Wave: hereinafter referred to as APW). This method is corresponding to the subjective rating well therefore it is suggested that this method can catch a psychological change. Furthermore it is shown that this method synchronizes with the result of the ride comfort by using response acceleration. Thus it is suggested that sensitive response MAP can be applied to the evaluation of ride comfort.

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In our daily life, we can keep standing without any consciousness, even when we are subjected to the base excitation such as earthquakes or train motions. However, from the view point of dynamic behaviors, the maintenance mechanism of standing state is not fully clarified. Especially for the elderly people, the risk for overturning increases due to decreasing muscle forces. And consequently, overturning will sometimes cause some difficulties in walking. Thus, it is very important to study the dynamic behaviors and the stability of the human in the upright position subjected to base excitations. In this study, the maintenance mechanism of standing state is investigated using a simplified dynamic human model. And the differences of the vibration response between the young and elderly people are studied. As a result, it is clarified that for elderly people, muscular loads on the waist and knee tend to increase, while for young people, those on the ankle tend to increase.

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Traffic jams and congestion are generated in various places like roads, festivals, disaster areas, etc. They cause mental stress and increase the incidence of traffic accidents. Thus, in designing environments in which people can move smoothly, traffic flow analysis is important. Currently, use of the micro model in pursuing individual particle behavior is common in traffic flow analysis. In this model, because the objects that become particles are capable of independent motion, the relation of action-reaction doesn't work between particles. Therefore, we constructed a micro-type pedestrian model in which particle behaviors depict a pedestrian's behavior characteristics in detail by the Distinct Element Method (DEM), and analyzed the traffic flow. In this study, to aim micro-type pedestrian model depicting the behavior characteristics in detail, model-enhanced DEM is constructed. The acceleration computation of the particle modeled in this model incorporate the Optimal Velocity (OV) model. After that the algorithm that can avoid even if a obstacle particle exists on the target direction was constructed and was incorporated in the 2D model. After that, the avoidance simulation, which takes into account the obstacle or other pedestrians, is done by using the 2D DEM-base traffic model. At the same time, an avoidance experiment similar to the simulations is done, and the effectiveness of the model is verified by comparing the results. As a result, the simulation showed similar behavior and velocity distribution to the experiment. Therefore, the effectiveness of the constructed traffic model could be confirmed.

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Human beings walk rhythmically. Passive dynamic walking is simulated such a human walking. Passive dynamic walking is very efficient, because it makes use of natural vibration of mechanical. The goal of this study is to realize more efficient and stable biped walking using natural vibration. In our previous studies, we proposed that the consistency of natural frequencies in swing and rocking is important for energy effective walking. In this study, Firstly, We make passive biped machine with subsystem which rotates like an upper body. This allowed the machine to walk longer distances with longer strides because the waist and free leg move in same phase. Next, We compensate for the damping of rocking motion. This allowed the machine to continue walking on flat floor. Finally, the local feed back controller mounted in DC motor which is fitted on each joint, it can realize walking which efficient as passive walking and stable.

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In walking analysis, which is one useful method for efficient physical rehabilitation, the ground reaction force, the center of pressure, and the body orientation data are measured during walking. In the past, these data were measured by a 3D motion analysis system consisting of high-speed cameras and force plates, which must be installed in the floor. However, a conventional 3D motion analysis system can measure the ground reaction force and the center of pressure just on force plates during a few steps. In addition, the subjects' stride lengths are limited because they have to walk on the center of the force plate. These problems can be resolved by converting conventional devices into wearable devices. We used a measuring device consisting of portable force plates and motion sensors. We developed a walking analysis system that calculates the ground reaction force, the center of pressure, and the body orientations and measured a walking subject to estimate this system. We simultaneously used a conventional 3D motion analysis system to compare with our development system and showed its validity for measurements of ground reaction force and the center of pressure.

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Although many wearable sensors have been developed or commercialized for gait analysis, ambulatory force sensors and motion sensors were rarely integrated to implement complete human dynamics analysis. Three-dimensional (3D) lower limb kinematic and kinetic analysis based on ambulatory measurements is introduced in this paper. We developed a wireless sensor system composed of a mobile force plate system, 3D motion sensor units and a wireless data logger. 3D motions of body segment and triaxial ground reaction force (GRF) could be simultaneously measured using the system, and the data obtained from sensor units on thighs, shanks and feet could be transferred to a personal computer by wireless local area network (LAN). An inverse dynamics method was adopted to calculate triaxial joint moments. The accuracy of kinematics and kinetics (joint moments) assessment is validated against results obtained from the stationary measurement system based on camera movement analysis and force plates.

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It is strongly required to reduce noise at moving person's ears in a noisy room by some active noise control (ANC) techniques. In the case of using fixed secondary sources, some multi-channel control methods are necessary. Various methods have been proposed for this on-line system identification, but it takes time to identify the error paths and the system can't follow quick movement of the error microphones, in the case of multi-channel system. On the other hand, Wave Synthesis (WS) Method is only useful for periodic noises, for example, purr of engines and tones of fans. But the feature of this algorithm is not to need the system identification of the error path. When error point moves, this algorithm can follow it. The single channel WS method has been developed and applied to purr of engines so far and has obtained great noise reduction. However, a multi-channel system using WS algorithm has not been established. According to these backgrounds, the final target of this research is to develop multi-channel WS ANC system and apply it to reduce noise at person's ears who move in a noisy room with periodic sound. In this report, at, first, we deduced multi-channel Wave Synthesis Algorithm. Next, we performed the experiment in the single channel system and checked convergence time. Consequently, it's confirmed that high order harmonics components decrease quickly. In addition we checked how quick to follow movement of the error microphone.

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Recent development of high-directional loudspeaker based on parametric array has allowed sound transmission within a narrow range of acoustic space like 'spotlight'. Parametric array utilizes the high directive characteristics of ultrasonic sound, where the embedded difference component of two ultrasonic carrier waves is expanded as audible sound. This peculiar characteristic can be implemented as one measure for improving active noise control scheme controlling acoustic field locally and efficiently. In the present study, a new approach for active control of sound field inside enclosure is investigated using high directional parametric loudspeaker as a control source. The sound field inside enclosure is formed by the incoming noise through an opening placed on one face of the enclosure. Two cases are tested experimentally: in the first case, both the control source and the error microphone are placed outside the enclosure, and in the second case, they are placed inside. It is known that in the latter case, the suggested ANC system using high-directional sound source can mitigate sound effectively in comparison to use of conventional omnidirectional loudspeaker.

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Magnetic resonance imaging (MRI) machine generates a noise which reaches 140dB at maximum level during a medical examination. The purpose of this paper is to control a MRI noise which transmitted from the scanning room by using active noise control (ANC) system with the piezoelectric (PZT) speaker. In the model experiments, semi-anechoic room is used to substitute for the MRI scanning room. The attenuation levels by the ANC system were measured, which using 1/1 octave pure tones of 125 - 4000Hz and the dummy MRI noise. In order to estimate the control effect, the distributions of equivalent sound pressure level around the door were measured by the line scanning microphone. The experimental results show that the transmission noise was attributable mainly to the leak noise from door, and the noise reductions at control microphone were obtained about 14dB by using the present ANC system. However, these reductions were only obtained at the near-field of control microphone, the transmission noise in entire field of the room could not be reduced.

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Active noise control (ANC) system with extremely high sampling frequency such as 100kHz was proved to be effective for reducing the distance between the reference microphone and the secondary source, by using Field Programmable Gate Array (FPGA), in our previous works. However it was difficult to reduce low frequency range by the above system, because it could not realize long impulse response. In this study, by using parallel computation technique of FPGA, long impulse responses were realized and the above compact ANC system was proved to be effective for low frequency range down to 200Hz.

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In this paper, a kind of active noise barrier (ANB) using active noise control (ANC) technique to improve noise insulation performance in low frequencies is proposed. The ANB consists of an ordinary noise barrier, three active noise control units (ANCU) and a DSP (IMS 320C6713 DSK). Feedback ANC system is used in the ANCUs. In order to achieve higher noise attenuation, fast transversal filter (FTP) adaptive algorithm is introduced into the feedback ANC system. Then, numerical and experimental study on an active noise barrier is conducted. As a result, the active noise barrier shows better noise insulation performance in low frequencies. Moreover, in this paper, basic concept of a new type hybrid ANC system which is a combination of the feedforward and feedback control structures is proposed. The feedback controller provides active noise insulation, and the feedforward controller whose reference signal is synthesized in the feedback controller cancels noise at a specific position where its error microphone is. Effectiveness of the hybrid ANC system is verified by experiment. The result shows that the hybrid ANC system can reduce noise better than single feedforward or feedback ANC systems.

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Local active noise control systems create a zone of quiet around a physical error sensor location. The zone of quiet is generally small, and as such, the physical error sensor is placed at the desired location of sound attenuation, which is usually inconvenient. Virtual sensing algorithms have been developed to aim for creating the zone of quiet at virtual sensor location that is remote from the physical error sensor. However the sound attenuation of the traditional virtual sensing algorithms worsen by change of primary source location that alter the transfer characteristics between a virtual sensor and a physical sensor. This paper presents a method to approximate the transfer characteristics between a virtual sensor and a physical sensor by superposition of several transfer functions calculated from acoustic paths using positional information of primary source. The transfer function is expressed a dead-time component and a coefficient vector for amplitude correction calculated by Maekawa's curve. The effect of control using the approximated transfer function in numerical simulation indicates that around 5dB of attenuation can be achieved.

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This paper describes psycho-acoustic experiments using online optimization in order to improve the performance of active noise control to modify noise into comfortable sound. Three comfortable sound parameters characterizing the artificially synthesized based on insect's singing are set as deign variables and the alpha wave components of the electroencephalogram measured after hearing the sound is set as the objective function. By using the simplex method the comfortable sound parameters are optimized during experiments. Since experimental results show that there exists optimum combination among the comfortable sound parameters, the comfortable sound plane is calculated as the optimum combination. After discussing multiple planes and dependence on frequency of sinusoidal function, active control experiments to modify machinery noise to comfortable sound are carried. It is confirmed that the proposed comfortable sound function improves the performance of the active noise control.

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As an adaptive algorithm for active noise control, LMS algorithm is most popular because of its simplicity and small calculation amount. However, LMS algorithm doesn't converge quickly and accurately because it needs high order of FIR model for colored noise, for example impact noise. For this problem, we propose a method using least squares lattice algorithm (LSL algorithm). LSL algorithm has high-speed convergence based on least-squares method, and accurate convergence by autoregressive moving-average (ARMA) estimation. Therefore, LSL algorithm is expected that it has quick and accurate convergence of ANC for impact noise. Also, we attempt to apply this LSL algorithm to a case close to actual environment. In this case, since the acoustic field has secondary path characteristic, the filtered-x algorithm is applied generally. However, filtered-x algorithm cannot apply to LSL algorithm directly because of it does not calculate FIR coefficients but ladder coefficients. Hence, We propose a method that do not use filtered-x algorithm, and show the effectiveness of that in computer simulations.

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There are many noise sources around us. Floor impact noise such as the sound of footsteps and falling object becomes a problem in an apartment house. Floor impact noise has a peak at the low-frequency range and passive noise control for floor impact noise is difficult to control. Therefore, the purpose in this paper is control the impact noise with active noise control. Since the impact noise comes separately, active noise control with LMS algorithm based on the steepest descent method is difficult to the extent of slow convergence characteristics. In this paper, the effectiveness of active noise control using frequency domain adaptive algorithm that has fast convergence characteristics is confirmed through simulations and experiments.

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On active noise control (ANC) in 3-dimensional acoustic field, a control effect becomes worse when an evaluation point moves. Against this problem, we proposed a control algorithm using filter map. Validity of this algorithm was shown by simulations and experiments. To use the method, however, the adaptive filters must be accumulated in a controller so that the required memory becomes large. We use an IIR filter in order to reduction the memory in this paper. The filter is configured by tapped-delay-line structure and lattice structure. Moreover, an algorithm for updating the filter is proposed. The validity of the algorithm and the filter is shown in numerical simulations.

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In three-dimension acoustic field, it is difficult to control the whole room using active noise control (ANC) technique. Instead, around-head-control is investigated in this paper. To realize around-head-control, it is necessary for a controller to follow the head movement. However, there is a problem that the control effect under the movement is worse, and the recovery of control effect after movement is slow in conventional ANC. Against this problem, we propose the new method of improving the adaptation speed. In the algorithm, the updating width appropriate to each coefficient of the adaptive filter is calculated by using a step size vector. The step size vector is calculated from the coefficient of adaptive filter before updating. The validity of the proposal method is shown by the numerical simulation and the experiment in anechoic chamber.

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This paper presents a new approach of active control of a window pane. This study can be applied to a window of a house or an office, producing a quite space in the adjacent room. To obtain a high performance of interruptive sound using a light weight material, the active vibration control of the material can be used to improve the transmission loss. The acoustic mode of the cavity greatly influences the window pane in the enclosure. Therefore, when applying vibration control of the structure, set up in the closed space, it is necessary to note the influence of the acoustic mode.

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A feedback control has an advantage in that it doesn't need a reference microphone. However, an usual feedback control system isn't obtained a control effect at an evaluating point apart from a control source. Nakashima et al proposed the feedback control system which can rise an output from a control source. It's called the distant control system in this paper. The effectiveness of this system has confirmed in numerical calculation that controlling at an evaluating point. Accordingly, when we actually confirmed the effectiveness of this system through the experiment, it improved a control effect 1.9 dB than usual at the evaluating point located 200mm from an error microphone. Besides, to expand the control area, we apply the distant control system to the multi channel control. A crosstalk canceller is introduced to the system for preventing a deterioration of a control effect due to a crosstalk. As a result of the measurment in the control area, we confirmed that the control area was expanded by the multi channel control.

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An automatically performing bell system, which informed the specified time with music, has many types of bell configuration and arrangement. The first requirement for the bell system is to tune the fundamental resonance frequencies of each bell to an equal temperament of scale. Finite Element Method was used to determine the natural frequency and mode shape of the axisymmetric bell. Experimental evaluation was also carried out to examine the existence of the orthogonal mode which frequency is close to the fundamental frequency. Boundary Element Method(BEM) was applied to investigate the acoustic radiation properties of bell's eigen mode. Based on this results, bell is approximated by the point sound source with specific radiation directivity. Moreover, wave form of sound pressure radiated from the vibrating bell is calculated by this point sound source approximation and compared with the detailed BEM analysis.

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In this paper, in order to solve the characteristics of the radiated sound field generated by vibration of a flat elastic single plate or double plates with different materials in small enclosure with rigid walls, we try to apply a numerical simulation technique using a finite difference time domain (FDTD) method to the coupled analysis of the vibroacoustic characteristics. The update equations for the FDTD simulation in the sound field and in the elastic body modeled by the isotropic material are coupled at the boundary of both the mediums. Numerical results show that the frequency response changes depend on the value of the material constant of the elastic plate and/or the volume of the enclosure. Since the experimental results using a vinyl chloride plate and an aluminum plate show the same tendency as the numerical results, the validity of the numerical simulation using the FDTD method proposed in this paper is confirmed.

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This paper describes the idea for reducing fan noise by structure-borne sound control. Firstly we develop a new method for identifying the contribution of structure-borne sound and air-borne sound to fan noise by using experimental statistical energy analysis (Experimental SEA). We had proposed the process for reducing structure-borne sound on machinery by using Experimental SEA. In this process we had developed the way to evaluate the sound pressure level s at the assessment points by considering only the structural SEA subsystems which are able to be carried out the countermeasure. We introduced the conversion coefficients of each structural SEA subsystem to the sound pressure at the points. The contributions of sturucture-borne and air-borne sounds are determined by using the experimental SEA model, the conversion coefficients and the subsystem energies in operation. This method is demonstrated to apply fan noise on PC.

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This paper describes the classification of the behavior of instantaneous longitudinal structural intensity on beam. Structural intensity is defined as the instantaneous rate of energy transfer per unit area of beam and is calculated by the product of stress and velocity. Then the stress and longitudinal velocity and structural intensity on a simple beam are calculated by using numerical simulation based on finite element method. We consider the two conditions in transient and in the steady state are considered to discuss the behaviors of the instantaneous structural intensity. As a result, the behaviors can be classified into three cases under the resonant with small damping, under the non-resonant with small damping, and under the large damping. In the transient condition there is no difference between the three cases. On the other hand in steady state condition, the phase difference in each case between the stress and the longitudinal velocity are different and then the structural intensity behaviors are different.

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Main causes of engine noise level and sound quality are piston slap, main bearing impact force, gear impact force, fuel injection pressure and valve train opening and closing force. This paper presents the theoretical procedure to predict the vibratory response and radiated noise of the engine block considering the dynamic effect of motion and impact vibration of components of internal combustion engine. Engine noise radiated from the engine block surface is evaluated using the acoustic radiation efficiency determined by Boundary Element Method and spatially averaged mean squared velocity of the engine surface. These method enables us to predict the engine noise in the early design stage. In this study, engine structure consists of piston, connecting rod, crankshaft, gear train shaft and engine block. Equation of motion of each structure is derived taking into account the inertia forces induced by vibration and constrained motion, external force, restoring force and reaction force at the connecting point. Modal analysis technique is employed to describe the equation of motion of each structure in the stationary and rotating coordinate and time history of vibration response is obtained by numerical integration technique. This method is applied to evaluate the vibratory response and radiated noise of actual diesel engine and its applicability is confirmed.

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The internal combustion engine sometimes 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. In this paper, impact vibration of cylinder liner is obtained by the simulation analysis and acoustic pressure in the cooling water passage is evaluated by FEM analysis which boundary conditions are vibratory acceleration and acoustic impedance of the cylinder liner and water jackets. The availability of these analytical procedures are discussed comparing the calculated and measured results of the vibration response of cylinder block and pressure response in the coolant passage occupied by the air medium.

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Prediction of structure-borne noise based on an analysis of vibration of structure has been a significant issue for railway viaducts. We have therefore developed a new method of vibration analysis based on a flexural vibration analysis extended to the whole of structure. As the result of the calculation and measurement of the vibration of the floor slab of a concrete viaduct constructed on Shinkansen line, it has been revealed that the developed method has acceptable accuracy. However, the method is a little bit complex because in the method, three layers, namely rail, rail-supporting layer and composite layer composed of the track slab and floor slab are treated as a three layered beam and a property equation of the three layered beam should be solved. In place of that, if each of three layers can be treated as an Euler beam, and only property equation of each beam individually should be solved, the analysis becomes simpler. In this paper, the substituted treatment has been examined and it has been revealed that the difference in accuracy between the solution of three layered model and that of the model in which respective beams are treated individually is substantially small.

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The drive-system noises of motor vehicles are composed of electric apparatus noise and mechanical gear noise. In recent years, the drive-system noise generating from the motor vehicles on the narrow gauge are decreased by adoption of the low noise traction motor. However, the sound of gear noise is increased relatively. The purpose of this paper is to investigate the fundamental noise characteristics of the vehicle gear systems. Therefore, we carried out the mechanical dynamic behavior analysis to parallel cardan driving gear device which consists of helical pinion and gear systems. Furthermore, we carried out FEM and BEM analysis to predict the sound power reductions of gear systems under a condition where the casting iron material applied to the device using the damping factor obtained from simple damping test. Consequently, in case of comparing with current one, we found that the gear case which apply to the material has decreased 2dB of sound power approximately.

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As the industrial diesel engine has the gear train to drive injection pump and valve system, engine noise is induced by the gear impact at the idling condition. Furthermore, gear impact noise is increased by the torsional vibration of the crankshaft. In this paper, numerical model of the torsional and bending damper for crankshaft is added to the total analytical system to predict the vibratory response and radiated noise of the engine block coupled with the rotating crankshaft and gear trains. The effects of the torsional and bending damper with scarce and sufficient damping to reduce the gear impact force, main bearing forces and engine block vibration are discussed.

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To analyze vibration transmission between the double walls in cars in the low frequency range, we applied a numerical method previously proposed by the authors. As a model for cars, we deal with mixed structures composed of a porous material sandwiched between a damped steel plate and a cover plate. Especially, we focus on the influences of beads in the damped steel plate on vibration transmission from the steel plate to the cover plate. The porous material on the top of the bead in the steel plate is removed locally corresponding to the height of the bead. Because of short distance between the steel plate and the cover plate in this region, vibration transmission through this region is investigated numerically. In our numerical method, we select displacement vectors as common unknown variable for the mixed structure including porous materials, viscoelastic materials and elastic materials. We solve under coupled condition. Further, explicit expressions of modal loss factor for the mixed structures are derived using asymptotic method. Using this technique, eigenvalue analysis and frequency response analysis are performed.

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Dynamic dampers are often used for suppressing vibrations of machines and structures. In this research, application of dynamic dampers to suppress sounds in a closed space such as cars and rooms is considered. For this purpose, effects of a dynamic damper composed of mass, spring and damping elements attached to a uniform sound tube is discussed. It is found that dynamic dampers can be used for suppressing sounds when the value of mass can be chosen small enough, contrary to the usual use of dynamic dampers. An iteration method for determining the optimal values of spring stiffness and damping coefficient is proposed.

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It has been increasingly demanded to reduce the noise along the railway lines because of speed-up of vehicle. High soundproof plates therefore have been desired to be installed over the existing concrete noise barrier to promote the performance to decrease the outside noise around the railway track. However, the higher wall which is applied to the viaduct cause the higher load and moment by wind, then it is almost impossible to install high soundproof plates without reinforcing the viaduct sufficiently. Therefore we have proposed a new soundproof system which consists of soundproof plate made of polycarbonate and its supporting frame. The top side of it is supported by a rotary axis, and the other three sides of it are held by the magnetic attractive force. The panel usually remains closed and will open in case of strong wind whose load is over 1.5kPa. In order to confirm the soundproof property when the plate is closed and whether it opens when strong wind blows, an acoustic test and a wind tunnel test have been executed. As the results, it has been made clear that the panel holds the same property as the normal soundproof plate when it is closed, and it actually opens when the wind which pressure is about 1.5kPa blows.

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Sound intensity method is one of the acoustic measurement techniques. Sound intensity means the propagation of sound energy and helps us to figure out sound field. Sound Intensity mapping is general measurement method that measures sound intensity vectors on each measurement points and combines the photograph of measurement field and measured sound intensity vectors. This measurement method has the problem that takes a long time to figure out sound field because of large amount of measurement points. If sound intensity vector is shown on measurement field directly aiming to find out the Noise Source, we figure out sound field quickly and simply. In this paper, all-in-one probe displaying sound intensity vector on measurement field was developed. The sound intensity probe consists of four microphones and the displaying device for sound intensity vector. The displaying device consists of LED array. In this report, the effects of the LED array structure to the measured sound field is investigated experimentally. This report demonstrates sound intensity mapping and noise source identification used the proposed probe.

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This paper proposes a method of acoustic vibration testing based on a point source generated by laser-induced breakdown. A high-power YAG pulse laser is used in this system for generating laser-induced breakdown in acoustic fields. Laser-induced breakdown is generated by reaching the local intensity of the laser beam for 10^9W/mm^2. For this reason, a convex lens is used to focus the laser beam. Laser-induced breakdown can be generated in arbitrary acoustic field by using varied convex lenses with focal length (spot radius). Therefore a speaker for conventional acoustic vibration testing has no use for installation in this method. The system is validated by comparing the resonant frequency of a micro space measured by laser-induced breakdown and calculated by theoretical model.

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The purpose of this study is to solve the structural noise level caused by electromagnetic force of coils, for front loading design the transformer noise. To research the phenomenon of the electromagnetic induced vibration, firstly, we observed radial and vertical direction vibration of coils, and we confirmed both direction vibration amplitudes almost same order. So, for the analysis of the electromagnetic induced vibration noise, we found the continuum mechanics model is necessary, and old analysis model using mass and springs, can not simulate the vibraion. Secondly, we made the proposed model of continuum mechanics and old model using mass and springs for a transformer, and calculate the vibration modes and responses of coils. The calculation results of the proposed model was good agreement with experimental results, but the old model was not good agreement. At last, we calculated the vibration level with the proposed model of the transformer and the tank, and the vibration level of the tank by coupled fluid analysis and structure born sound analysis. And we calculated the noise level around the tank which equipped the transformer with the boundary element analysis. Considering the vibration mode differences between calculation model and practical model, we could analyze the noise level within 5dB error. And we become able to get the highest level if the vibration mode agree with 2 times of the driving frequency when we design the transformer.

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With a recent size and weight reduction of electrical transformers, acoustic noise from transformers is likely to increase in a zone of audibility. Underlying technology for the acoustic noise reduction is required. Electrical transformers consist of iron cores, coils, tanks, frames and other structures. These vibration mechanisms and propagation path are unexplained clearly as a sound source. Investigation for each vibration characteristic is required to reduce the acoustic noise. In particular, as a sound source of electrical transformers, Understanding characteristics of an iron core are important. Experimental Modal Analysis (EMA) for a laminated iron core is performed with an impact hammer. EMA gives us the natural frequencies and vibration modes to reduce acoustic noise. Also we investigate a reliability of the Finite Element Method (FEM) models.

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While environmental issue, typically global warming is attracting attention for industrial machinery systems, the expectations of environmentally friendly industrial machinery have been increasing from various perspectives. These expectations include not only reduction of size, weight and electricity consumption, but also reduction of acoustic noise. In acoustic noise of industrial motors, in particular, an electromagnetic acoustic noise is jarring in a zone of audibility. An electromagnetic noise is likely to increase when frequency components of the electromagnetic force stimulate natural frequencies of a motor. In order to avoid the resonance with natural frequency, machine designers have a strong demand for accurate calculations for these natural frequencies in a design phase. Anticipating this demand, this paper studies a simulation method to estimate vibration characteristics of a rotor assembled in a motor.-

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Because the substation had come to be built in the city, the noise reduction technology of the power transformer came to be demanded. About the noise decreasing technology of the power transformer, the soundproofing technique of the tank, the vibration decreasing technology of the core and coil have been announced. However, neither the vibration property of the tank nor distributive characteristics of the noise in the tank are clear when energizing to the power transformer. This paper reports the results of measurement about vibration property of the tank and the sound intensity on energizing to the power transformer. Also we investigate the reliability of the Finite Element Method (FEM) model and the Boundary Element Method (BEM) model constructed by using the results of a measurement.

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Currently, automobile window panes are commonly adopted as single layer plate structure with glass material. Polycarbonate (PC) laminates offer the possibility of designing strong and light weight panes application in automobile. However, the acoustical properties of PC pane is very poor than glass pane because of its high rate of stiffness to low weight. This research is desire to develop new sandwich structures with PC pane for noise insulating instead of single layer glass pane. The sandwich structure consists of two thin laminates plates of the same PC material and a thin thickness lightweight damping core bonded between those plates. In this paper, sound transmission loss is calculated using decoupled equations representing symmetric and anti-symmetric motions for a sandwich PC pane. The effects of various structural and material parameters on sound insulation performance are investigated by means of numerical calculation. Predicted results show that sandwich PC pane has higher transmission loss at interested frequency range with possible compact thinner thickness.

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In the present paper, vibration properties of mirror foils installed in a hard X-ray telescope (HXT) on-board a satellite were investigated. Vibration tests and FEM analysis of mirror foils installed in the part model of HXT were conducted. From the experimental results, it appeared that the mirror had resonant frequencies at 64, 73 and 11 OHz. The modal shapes of 64 and 73Hz showed that the maximum amplitude appeared at edges of the foil. On the other hand, vibration amplitude became maximum at the center in the modal shape of 11 OHz. Experimental results of frequency responses of these modes agreed well with analytical results except around 64Hz. It is considered that the resonant mode of 64Hz was strongly affected by nonlinear characteristics of friction constraint between the foils and HXT housing.

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Transmission loss is a popular evaluation indicator of sound insulators. It is measured in reverberation room method with high cost. The mass law with considering the coincidence effect is commonly used to predict the transmission loss for homogeneous walls. However, they are derived qualitatively and based on simple assumptions. In this paper, we propose a method to predict the transmission loss by using the modal analysis. The reverberation rooms are modeled as cubic sound fields and sound insulator as a simply supported elastic plate, and the sound pressure in sound source room, the vibration of the plate, and the sound pressure in the sound receiving room are calculated. From the sound pressures in both rooms, the sound pressure level for each 1/3 octave band and the transmission loss are obtained. The effectiveness of the proposed method was verified through the comparison among the results of actual measurement, proposed method and mass law.

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Recently, the demand for the loudspeaker with sharp acoustic radiation directivity has increased to have to transmit the guide and the explanation to many and unspecified persons selectively in the library, the museum, and the amusement facilities. The purpose of this study is acoustic radiation control by the changing design factor of the PZT loudspeaker. Our past study, it confirmed that acoustic radiation directivity changed by moving oscillator position. In this paper, vibration analysis is carried out to observe modal shapes of vibration board. And, PZT loudspeaker is driven some frequencies which gives modal shapes, and measured acoustic radiation characteristics with microphones. In order to considerate a relationship between modal shapes and acoustic radiation, numerical analysis by the Rayleigh integral method are carried out. Results of flat diaphragm analysis show that acoustic radiation characteristics are according to modal shapes in low frequencies. And numerical analysis was corresponding to the outcome of an experiment in up to about 1300Hz.

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Noise reduction in cabins of tractors and construction equipments is required. The standard antinoise techniques are categorized into vibration isolation or sound insulation treatment of the panel, and acoustic absorption in the cabin. In this research, a technique is developed to estimate the noise source locations and the contribution ratio of each path by using reciprocity theorem, because the contribution ratio of each path is difficult to identify in the experiments. The cabin noise is divided into three paths: transmission sound through windows, leakage sound from open space, and structure-borne sound through rubber vibration isolators.

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Experimental Statistical Energy Analysis (ESEA) is applied to analyze the vibration energy flow on violin body. The violin body is subdivided into 6 SEA subsystems. The analysis can identify the power flow through the subsystems and the power input into each subsystem during the impact excitation at the bridge which connects the strings and the body. The analysis results for two kinds of violin are compared. It is shown that three pieces of knowledge concerning on the better violin are obtained, 1) damping of the body structure is small, 2) the frequency distribution of power input into the body is in inverse proportion to square root of frequency and 3) the energy on the top plate is propagating through the sound post into the back plate. The fundamental discussions on the knowledge 2) and 3) are carried out.

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This report is about proposal of identification method for SEA (Statistical Energy Analysis) parameters using FEM considered coupling in damping. Usually, damping is influenced by shape of panels and forms of the connection. Therefore, we propose a new identification of SEA parameters for internal loss factors using FEM considered in damping. We verified using the model, which considered three panels connected in U-shape with viscoelastic damping layers. As a result, we could identify the SEA parameters in high precision. And the proposed SEA enables us to improve not only precision in high frequency but also precision in low frequency.

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A bicycle is a popular vehicle for a lot of people by the low price and the easy maintenance in comparison with a car and a motorcycle. In order to expand the popularity of the bicycle, improvement of the ride comfort is necessary. In this study, to improve the ride comfort of a utility bicycle, subjective evaluation tests and acceleration measurements were performed. In the subjective evaluation test, the vibration feeling of the seat and the ride comfort of bicycles were evaluated by using five kinds of bicycle. And the vibration accelerations of the seats were measured and frequency analysis was performed to obtain which frequency band has high contribution to the ride comfort. As a result, low frequency vibration of the seat was clarified to have high contribution to the ride comfort. Next, the seat vibration reduction was tried. For decrease of the seat vibration, the spring rate of the seat was reduced. As results, the acceleration level was decreased in the running test and the ride comfort was improved.

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Accurate rigid body property (RBP) identification is desired in various industrial fields such as aerospace and automotive engineering. In a past study, our group developed a new identification method based on a gravity-dependent suspension model using multiple elastic wires. The identification method enables to obtain the RBP of mechanical structures with high accuracy. However, the problem of measuring errors due to the elastic modes of mechanical structures still remains in this method. In this research, in order to accurately identify the RBP of low-rigidity structures, new two methods which combine the suspension model and modal analysis of the elastic modes are developed from the previous one. These methods are classified into two groups of least-squares optimization models, the "Single-step Solution Gravity-dependent Suspension Model" and the "Modal-step Solution Gravity-dependent Suspension Model". The validity of each model is confirmed by conducting experiments using low-rigidity structures.

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In this study, an accuracy evaluation index for running transfer path analysis (TPA) employing principal component regression method was considered and the reliability was verified. To evaluate the TPA accuracy, the consistency of response signals in which the calculated response signal by the TPA was compared with the measured response signal was used frequently until now. Also, the condition number that indicates the inverse matrix condition applied in the principal regression analysis was employed in some cases. In addition to these accuracy evaluation methods for running TPA, correlated principal component number (CPCN), that indicates the number of vibration mode correlating with the response signal generated at the running test, was proposed. The reliabilities of these accuracy evaluation methods were verified through simulations. As results, the conventional two methods (consistency method and condition number) could not evaluate the accuracy well. However, CPCN index could indicate the frequency bands where the TPA accuracy was high or low. Consequently, the new index was found to be a suitable index for accuracy evaluation of running TPA.

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It is very important to grasp the dynamic characteristics of machinery. Modal analysis is widely used as a basic technology for machine design. Various methods to identify the modal parameters of structures by the vibration test have been proposed. Recently, the frequency domain subspace method has been developed. Generally, it is easier to overview the dynamic properties of structures in frequency domain than in time domain. Therefore the frequency response functions (FRFs) are employed. In this paper, the modal parameters are identified by the frequency domain subspace algorithm. Then the residual terms derived from rigid body motions are considered. The effects of translation and rotations of the test specimen are investigated. The proposed procedure has an iteration process to modify the residual terms. The identification procedure is applied to an aluminum circle plate with a hole.

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In order to reduce the noise level in the cabin, it is important to extract the characteristics of acoustic system (dynamic properties of the cavity). When frequency response functions (FRFs) of the acoustic system are measured, acoustic excitation by an audio speaker is generally used and its capabilities have been already illustrated. However, to expand the availability of the acoustic excitation, it is necessary to reduce the number of excitation points and to predict the FRF with respect to the point where it was not actually excited (the unexcited FRF). It has been well known that in order to predict the unexcited FRF, a set of modal parameter can be used, where the auto FRF is thought to be included in the data set. However, for the acoustic system the auto FRF is hardly measured because the speaker is not able to apply the excitation at an exact point, but to apply a volume velocity at a small area. Therefore, this paper presents a new method to predict the unexcited FRF under the condition that the auto FRF is not included in the data set. In this paper, modal parameters of the acoustic system of a real automobile cabin are estimated, and the FRF is predicted by the proposed approach. The predicted FRFs are compared with the measured FRFs.

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