The particle damping system was investigated experimentally and theoretically. Particle dampers are passive damping devices and consist of a cavity partially filled with granular materials attached to a primary structure. The collision of granular materials with the wall of the cavity is results in an exchange of momentum and some energy dissipation of the primary system. Although their construction is simple and their effectiveness is essentially independent of temperature, particle damping is a very complicated phenomenon and remarkable nonlinear behavior. In this paper, a computational method for conducting simulations of particle damping was proposed. This method was based on the concept of an equivalent single-particle impact damper. The contact force model for representing the collision between a particle and the wall of the cavity was based on the work by Hertz, utilizing the theory of elasticity. In addition, the damping force was given, considering a fully plastic contact. The granular materials used in this study were glass beads and copper beads. Also, the mass ratio was set to 5% and 10% for glass beads and 10% and 15% for copper beads. The validity of the analysis method was verified by comparing the analysis results with the experimental results. It was found that an analytical solution is provided to estimate, with reasonable accuracy, the response of the primary system.

This paper deals with vibration damping analysis using finite element method with Model Strain Energy Method for T-shaped steel structure having Krylov type of acoustic black hole. On the region of the acoustic black hole, viscoelastic vibration damping material is laminated. The T-shaped structure is fixed all edges except one edge where the acoustic black hole exists. The damping layer is modeled by linear solid finite elements in consideration of complex modulus of elasticity. We calculated modal loss factors and eigenmodes including coupled deformations among substructures in the T-shaped structure. We clarified effects of an Acoustic Black Hole on the modal damping for each eigenmode.

This report is about response analysis using Statistical Energy Analysis（SEA）with FEM for two panels connected in L-shape with an acoustic black hole containing residual thickness. One end in the L structure is fixed. And other edges have free boundaries. Usually, modal damping is influenced by shape of panels and forms of the connection. Therefore, to consider coupling in damping between substructures, we use FEM and MSE（Modal Strain Energy）method to identify internal loss factors. Effects of the acoustic black hole containing residual thickness on the SEA parameters are studied. And for these cases, the proposed SEA enables us to improve not only precision in high frequency but also precision in low frequency.

This paper describes dynamic responses of alive human palms to receive moving objects with / without visual information. We measured transient responses when a levitating block collided with the palms. The impact force is measured using Levitation Mass Method (LMM) proposed by Fuji. Then, experimental results were simulated by numerical analysis using FEM. To reproduce behaviors of palms of living bodies, they are modeled using nonlinear complex restoring force element. This nonlinear complex element including positive / negative nonlinear hysteresis is attached to the block modeled with solid finite elements. The experimental data were compared with calculated ones.

The purpose of this study is to investigate numerically the static and dynamic characteristics of a shape memory alloy (SMA). In the previous study, we have proposed a vibration isolator using a post-buckled shape memory alloy, and pointed that it is expected to improve the isolation performance utilizing the negative tangent stiffness of post-buckled SMA and to mitigate the design requirement for the isolator. However, the mechanism and property of the negative tangent stiffness in post-buckled SMA, which is important for designing an isolator using post-buckled SMA, has not been clarified. Therefore, in this study, we investigate these characteristics by numerical analysis finite element method. Firstly, the static restoring force of post-buckled SMA was investigated. From the numerical result, the negative tangent stiffness of post-buckled SMA was observed and it was confirmed that the negative tangent stiffness arises when the phase transformation from austenite phase to martensite phase begins. The volume percent of martensite phase in post-buckled state was also clarified. Subsequently, the dynamic response of SMA was investigated. From this numerical result, it was confirmed that dynamically loaded SMA exhibited different behavior from that of general steel material.

In active noise control，if total acoustic power is minimized，absorption and blowout of acoustic energy around the control source are balanced，and a zero power phenomenon occurs in which the time average of control power becomes zero. In this research，we aim at generalization of the said phenomenon，and consider the generation condition of the zero power phenomenon in the case of multiple control sound sources. Next，based on the derived control rules，we will clarify the change in acoustic power due to the increase in the number of sound sources and the position from the viewpoint of numerical analysis. Finally，the zero power control law in the case of expanding the control sound source to n control sources is derived.Numerical analysis using the derived control law to prove importance.

If oil droplets are present in an oil-soluble medium such as fluorocarbon gas, it is expected that the sound attenuation will be increased by the dissolution of the gas into the oil droplets. In this study, we model this phenomenon as a multi-degree-of-freedom system consisting of mass point, connecting spring and connecting damping. In this model, the effect of gas penetration into oil droplets is taken into consideration by the connecting spring and connecting damping. Furthermore, by conducting experiments using a shock tube in which oil droplets are sprayed to fluorocarbon gas and comparing the attenuation ratio due to acoustic free vibration with the analysis results of a concentrated mass model, the sound attenuation effects by oil droplets and the validity of the proposed model check effect by oil droplets and the validity of the proposed model Check.

In architectural acoustics, accurate predictions of floor impact sound are important because the transmission of sound in buildings can have a great influence on well-being. We propose a new numerical method for accurately predicting floor impact sound and present several numerical examples. Typically, floor impact sound levels are predicted using finite element methods (FEMs) and the authors have previously developed a simplified method for predicting sound from the vibration response characteristics of structures. In general, beams and floor slabs are modeled in FEMs by using beam, plate and shell elements. However, solid elements should be used in a strict sense because they vibrate non-uniformly in the thickness direction. Unfortunately, this leads to high computational costs and possibly locking phenomena. One possible solution to this problem is to use higher-order elements. Spectral element methods (SEMs) offer the possibility of using elements of arbitrary order. The new method we propose is formulated as an SEM with high order solid elements. Part of a building, comprising some columns, beams and floor slabs, is analyzed using the new method and the vibration response characteristics is computed. The numerical results are in good agreement with measurements and the computational effort required is about half of that consumed by the conventional FEM using quadratic solid elements.

Development of sound and vibration analysis method for comprehensive mechanical structure has been highly demanded in recent years. However, it is difficult because characteristics of each part influences each other interactively, and it complicates the vibration power flow. To solve the problem, authors have been developing expansion of Statistical energy analysis (SEA) for solid structure, although conventional SEA have been developed for beam and shell structures. In this research, expansion of coupling loss factors, one of SEA parameter, for solid structure is proposed and its validity is shown through numerical simulation using FEM models; coupling of two beams, coupling of two thin plates, and coupling of two thick solids. By comparing vibration energy propagation between FEM, original SEA (for beam and shell), and expanded SEA (for solid), feasibility of proposed model is shown for predicting vibration energy between solid bodies especially in high frequency bands, while original SEA is more sufficient. Also, energy propagation between plate and solid coupled system is considered.

The main topic of this study is a shape design of a noise eliminating duct with an acoustic metamaterial using topology optimization. Topology optimization attracts attention as a useful technique because of its flexibility in the design and applied to the various fields. Focusing on the acoustic field, there are some studies on the optimization design for noise cancellation device of radiated noise from a pipe used by topology optimization. This paper presents a noise eliminating duct with an acoustic metamaterial using topology optimization based on normalized Gaussian network and genetic algorithm. The optimized shape of an acoustic metamaterial device presented sound wave deflection by controlling reflection wave at specific frequency.

Broadband dynamic absorber is proposed by authors, which is a beam, or a plate added on to a main structure and enable its vibration reduction. Vibration reduction in broadband frequency is demonstrated in previous study but its detailed mechanism is not explained yet. In this study, clarifying mechanism of broadband dynamic absorber is targeted to design an appropriate absorber for an arbitrary system. As an example, vibration reduction of a uniform beam with a simple beam shaped broadband dynamic absorber is demonstrated through numerical simulation. To clarify the difference and common points of broadband dynamic absorber and conventional dynamic absorber, pseudo modal model, diminished simplified model, of broadband dynamic absorber is modelled. By comparing the vibration reduction effect of the broadband dynamic absorber with the vibration reduction with conventional dynamic absorber, the mechanism of broadband dynamic absorber is investigated that each translational and rotational mode performs as dynamic absorber respectively, so vibration reduction in broadband frequency is achieved. Further, it is suggested that pseudo modal model is similar to multiple dynamic absorber, so the design procedure of multiple dynamic absorber can also be applied on the optimization design of broadband dynamic absorber. Even so, it is difficult to handle all modes especially in higher frequency range. In those cases, vibration energy propagation analysis are still effective tool.

This paper describes hybrid vibration analysis using Statistical Energy Analysis（SEA）and FEM for two panels connected in L-shape with an acoustic black hole having a damping layer. All side edges in the L structure are fixed. Usually, modal damping is affected by not only shape of panels but also their boundaries. Thus, to account for couplings in damping between substructures, internal loss factors are evaluated using FEM and MSE（Modal Strain Energy）method. To clarify wave propagation, coupling loss factors are identified. Effects of the acoustic black hole with fixed edges on these SEA parameters are studied.

In order to reduce gear noise, it is general to perform processing such as shape correction of the gear contact surface. However, there is a problem that the processing cost increases. We are developing a method that enables low noise reduction at low cost by taking advantage of the damping characteristics of the gear material without changing the shape of the gear contact surface by machining. High strength ferrum casting ductile (H-FCD) has the same strength as conventional gear materials and has high material damping performance. Furthermore, the conformability of the tooth surface is also good. The amount of time history reduction of noise is large, and it is possible to omit the tooth grinding process which occupies much of the gear manufacturing cost. In this report, we first compared the material damping characteristics of general steel and FCD by exciting a simple plate. Next, the effect of gear lubricant oil on noise was evaluated by a rotation test of the H-FCD practical use gear.

It is necessary to estimate noise generated from various machines for noise control. The vibration analysis of structures is important to estimate noise power radiating from the structures. Almost machines are composed of not only simple flat plate but also thin plate structures which has a convex. In general, the vibration analysis of these structures can be achieved by FEM. However, FEM is not suitable for structural optimization to reduce vibration or noise because of its huge calculation cost. In this paper, a new analysis of these structures with the Rayleigh-Ritz method is proposed so as to reduce calculation cost. Two models for vibration analysis using the summation of multiplication of eigenfunctions of Euler beam as trial function. First model called as “the adding beams model” which the boundary of convex changes to beams is introduced and its strain energy and kinetic energy of beams by bending and twisting are additionally calculated. Second model called as “the convex strain model” in which the strain by bending and stretching of upper plane and side-wall of convex are taken into account is introduced. Through these two models, the approximate vibration analysis of convex plate can be achieved. The calculated natural frequencies and mode shapes of the proposed analysis are compared with those obtained with a commercial FEM software (ANSYS). The result of the adding beam model agrees well with that of FEM. On the other hand, the result of the convex strain model has large error because the trial functions may not be enough to represent the model shape of plate with a convex.

Suppression of noise and vibration in machine products is an important problem, and many methods have been studied. In particular, structural-acoustic coupled effects due to the weight reduction of machines cannot be ignored. Therefore, research on efficient analysis methods for coupled systems is required. In structural-acoustic coupled analysis, the finite element method (FEM) that the acoustic space is described by sound pressure and the structure is described by displacement is often used. In this method, eigenvalue analysis requires a long computational time because the mass and stiffness matrices are asymmetric. In our previous study, we proposed a concentrated mass model (CMM) of quadrilateral elements for two-dimensional acoustic space. This model consists of mass points and connecting springs, and has variable displacement in its acoustic space. Since the CMM has symmetrical mass and stiffness matrices, structural-acoustic coupled analysis can be performed efficiently. The effectiveness of the CMM was shown in the past for an acoustic space-membrane vibration coupled system. In this paper, we propose the CMM of arbitrary element shape in structural-acoustic coupled analysis. Furthermore, we propose a coordinate transformation method to improve calculation speed by reducing the degree of freedom while preserving the symmetry of coefficient matrices. The effectiveness of the proposed method is confirmed by numerical calculation.

Beams with folds may have mode of vibration with locally large amplitude. This paper proposes a design method to give vibration modes having a large amplitude at desired position and desired natural frequency for a folded beam. The method consists of two steps. In step 1, focusing on the waves propagating in the beam, the position and angle of the fold are determined from the increase and decrease of the wave at the fold. Wave vector is introduced in order to deal with waves propagating through the beam. It is possible to determine design variables sequentially by the assumption to avoid numerical instability caused by evanescent waves. In step 2, numerical optimization is performed to match the natural frequency to the desired frequency. The validity of the proposed method is confirmed by designing several folded beams.

Analytical Statistical Energy Analysis (Analytical SEA) examines coupling loss factor (CLF) between same dimensional subsystem such as between beam and beam, but not enough between different dimensional subsystem such as between beam and plate. And there is no article on the effect of hollow beam cross section deformation on vibration and noise. This paper applies analytical SEA to vibration propagation between hollow beam and plate at frequency without cross section deformation. Then an optimization is carried out structure with a mixture of beams and plates to Check its validity. A test structure is a hollow beam and a plate connected. At first vibration characteristics of the test structure are evaluated by FEM and it is shown to be divided into three types of predominant modes. Then most effective excitation direction in the vibration propagation from the hollow beam to the plate is evaluated, indicating that it is the same direction as the out-of-plane direction of the plate. Then CLFs of the test model is calculated by FEM-SEA and analytical SEA. It is shown effect of cross section deformation and both analytical SEA evaluation formulas are applicable. Finally, based on the findings obtained by the test mode, simplified model of a car frame and floor is Optimized by analytical SEA. and confirmed the vibration reduction effect using FEM.

In recent years, demand for a toilet noise reduction has been growing with an aging of population in japan. The purpose of this study is to develop the active noise control (ANC) system for a toilet noise. We proposed the toilet seat ANC system, in which the control sound is radiated to the inside of toilet bowl through the slit hole of the toilet seat. In this paper, the effectiveness of this proposal system is experimentally examined in the case of closing the lid of toilet. In the experiment, measurement of noise reduction characteristics and the sound visualization of toilet model using probe microphone were carried out. The results of this study shows that the noise-reduction effect was obtained about 5-20dB at the measurement microphone, in control for pure tone. From the result of sound visualization, noise-reduction effect was obtained in the local space of the error microphone position, however in external sound field, noise-reduction effect was hardly obtained depending on frequency due to the influence of transmission sound from the internal sound field.

In conventional active noise control (ANC), the sampling frequency of controller is determined so that the Nyquist frequency is higher than the highest frequency of noise. This setting is not efficient for cost when the noise is narrow band noise. In this case, the sampling frequency can be lowered to control. However, it is necessary to shift the noise frequency below the Nyquist frequency. In this paper, to control narrow band noise, heterodyne is used to shift the frequency of noise. By using heterodyne, frequency band of some signal can be shifted to lower and higher frequency band. To use the lower band in the A/D converter, a low pass filter is placed in the previous stage instead of anti-aliasing filter. On the other hand, in the latter stage of the D/A converter, to use higher frequency band, a high pass filter is placed. This method can be used conventional adaptive algorithm, because it is not adaptive update method but input and output method (in other words, control band choosing method). The validity of the proposed method is shown in numerical simulation and experiment. The results show control effect can be obtained for noise above the Nyquist frequency by proposed method. Moreover, it is shown that band stop performance of high pass filter is dominant for control efficient.

Plate-cavity models have been investigated by many researchers in order to verify active minimization of acoustic potential energy in the cavity or structural kinetic energy of the plate. Structural modes of the plate can be manipulated by control forces to minimize the acoustic potential energy or structural kinetic energy. However, it is not straightforward to interpret the modal behaviors, because the structural modes couple with each other in such structural-acoustic coupled systems. Recently, structural modal acoustic potential energies have been formulated in order to facilitate to independently evaluate a contribution from each structural mode to the acoustic potential energy via interaction between structural modes. In this study, structural modal acoustic potential energies before and after control are analyzed by computer simulation, and the control mechanisms are interpreted by observing the modal behaviors.

In previous work, the authors have proposed the earplugs that pass a specific frequency of sound, with simple structured analog acoustic band pass filters consisting of a micro-orifice, a flexible elastic plate and a small weight. These earplugs could efficiently let workers in noisy factories to protect their ears and, at the same time, to hear the necessary sounds for communicating with colleagues, noticing danger alarm sounds, and detecting equipment failure noise, etc. In this study, to evaluate the influence by acoustic properties of individual ear, the insulation performance of the suggested filtered earplug are calculated and measured in the cases of using an occluded-ear simulator and a simple straight pipe coupler. The calculation model of the insulation property of the proposed earplug is derived with the transfer matrix method, considering the acoustic transfer impedance of the ear simulator, which is specified in IEC 60318-4 (2010). The results in calculations and experiments are closely matched and that shows the validity of the calculation model. These experimental and calculation results also confirm that the proposed earplug has the function to pass a specific frequency of sound even in actual use. Furthermore, it is considered that the proposed earplug may have the robustness to the differences of the acoustic properties of individual ears.

Bone conducted ultrasonic (BCU) is expected to apply to hearing aid device for sensorineural profoundly deaf people. This device can equip excluding a head. The purpose of this study is to design the neck mounting type of the BCU hearing aid device which is able to control a sound image localization in auditory sensation. The BCU hearing aid device is constituted by the bimorph piezoelectric vibrator and the mounting device, which is produced experimentally. This BCU hearing aid device can mount on the sternomastoid and the trapezius. In the experiment, the effects of these mounted position on the direction and the angle of sound image localization are evaluated sensuality. The experiment result shows that the sternomastoid and the combination type could control the sound image localization of the crosswise direction. The experiment result also shows that the trapezius could grasp of the crosswise direction is possible.

When we usually play the classical guitar, we give the impulse excitation to the string using the top of finger and the nail. So, it is difficult to get the enough volume and extension of a guitar sound. It is an important subject to bring the characteristic guitar sound with the wide variety of the tone color as far away as possible. The tone color of guitar is defined as the pattern of the envelope curve joining the peak points of the exciting harmonized frequency. The time series of keeping the envelope curve pattern is estimated for the extension of the tone color. Here, we study the behavior of the extension of the guitar tone color.

Guiding chime is an acoustic welfare device for visually-impaired person, which is informed a direction of ticket gate of station by using guiding sound. However, direction inductivity of current product is insufficient, and it becomes a noise pollution to a station employee or user. Therefore, the purpose of this study is to design a directional speaker which is specialized to reproduce a guidance sound. In the experiment, thin flat panel type piezoelectric speakers using three vibrators was produced experimentally in order to design the sound directivity. The acoustic characteristics of speaker were evaluated by the frequency response measurements, and the sound directivities were evaluated by the radiated sound field visualization measurements. The results of this study shows that the prototype speaker could well reproduce 800Hz octave-band, which is important to recognize the guidance chime sound. And the sharp directivity of radiation sound was observed only at the direction of rectangular long-side of prototype speaker.

In recent years, the reduction of CO2 emissions from transport equipment has been required. Even in marine engines, energy saving measures such as longer stroke (lower engine speed), maximum pressure in the cylinder, and electronic control have been taken. However, these measures generally tend to increase the engine excitation force, and increase in torsional vibration is a problem in propeller propulsion shaft systems. In this paper, a simplified mathematical model was derived for the torsional vibration caused by engine torque harmonics in the propeller-engine propulsion shaft system of a ship. By performing theoretical sensitivity analysis using this model, the effects of engine inertia moment adjustment with a tuning wheel and intermediate-shaft stiffness adjustment used as a measure to reduce torsional stress at torsional resonance are clarified. Moreover, the sensitivity equation obtained was compared with the numerical analysis results to verify that it had sufficient accuracy.

I am now developing a new sound localization method, Double Near-field Acoustic Holography (DNAH) method. This method is aimed to improve the resolution of low frequency sound localization. This DNAH method is converted method of conventional Near-field Acoustic Holography (NAH) method. The NAH method is said as it has best resolution in the current sound localization methods. However, the resolution of low frequency sound localization is not enough to localize the position of sound sources. In the former paper, the improved resolution of DNAH method in low frequency sound localization is proved by numerical simulations and basic experiments with speakers. By the basic experiments, the reconstructed images by DNAH method show better resolution than the images by NAH method.

In this presentation, the measurement for an actual commercial product, a window type air conditioner, was carried out. In this experiments, the images by proposing DNAH method shows the sharper image than the images by conventional NAH method. As a result, it is proved that the proposing DNAH method is effective for low frequency sound localization for the real mechanical products.

A Perforated plate is used as an acoustic absorption material for compressors and acoustic barriers for roads and railways. There are many studies of the perforated plate from the aspect of the acoustic absorption. In this paper, the effect of set positions of the perforated plate on the acoustic natural frequency is considered with the TMM and the experiment. And the reason why the analytical result due to the TMM and the equation of Melling are in good agreement is clarified. From the analytical and experimental results, it is clarified that the smaller the aperture ratio becomes, the lower the acoustic natural frequency becomes with increasing of the hole length of the perforated plate. And the set position of the perforated plate can control the excitation of an acoustic specific mode. And the TMM is useful for obtaining the acoustic natural frequency, because the imaginary part of the acoustic impedance of an orifice obtained by Melling coincides with the analytical result by the TMM.

This paper is concerned with active control of acoustic radiation power of a multi-walled structure. In the past literature, optimal control of acoustic radiation power for a double-walled structure in which both walls of the acoustic space are surrounded by flexible walls has been studied. It has been clarified that the reduction level of an actively controlled double-walled structure is greater than that of an actively controlled one-walled structure in the sense of sound transmission control. Thus, the number of flexible walls have an impact on the control effect. However, research on modelling and control of a triple or more walled structure have not sufficiently done. Therefore, this paper presents how to model and control a triple walled structure. First, the target structure is analytically modelled by using modal coupling method that utilizes modal amplitudes of the uncoupled subsystems. Next, the optimal control law for minimizing the acoustic radiation power of the triple wall structure is derived by using the elementary radiator method which calculates the acoustic radiation power based on the minute and divided elements of the panel. Finally, numerical simulations of the control system are conducted, confirming the effectiveness of the proposed method.

There are various technologies for levitating and manipulating objects. For example, there are technologies using magnetic force or optical radiation force. In these technologies, the target objects are limited to magnetic materials or transparent dielectrics. On the other hand, the technology using acoustic radiation force can be applied to almost all solids and liquids. This technology is called acoustic tweezers. Acoustic holography has been studied with regard to acoustic tweezers. Acoustic holography is one of the methods to generate acoustic tweezers. In this method, many ultrasonic transducers arranged in an array are used. By adjusting the phase of each ultrasonic wave, various force fields can be generated and levitation objects can be realized. One of the problems of levitating objects using acoustic holography is that detailed performance such as the limit of size and weight of the target object has not been clarified. In order to solve this problem, it is necessary to establish a design method and to verify the performance of levitation experimentally. In this study, we designed the experimental device in order to use acoustic holography, and experimentally verified the performance of levitating objects by using the device. The experimental device we designed has 49 ultrasonic transducers, and each transducer can be driven with different phase and intensity. Therefore, acoustic holography can be used by using this device. First, we evaluated the feasibility of levitation by using objects of various densities and diameters. As a result, levitation was realized when the density of the objects were 23.5 kg/m³ or less. Second, we conducted the experiment to examine the relationship between the levitation height and the diameter of the object. As a result, it was found that the smaller the diameter of the object with respect to the wavelength, the higher the levitation height.

In order to reduce machine vibration, it is useful to estimate the excitation force as well as grasp the vibration characteristics of machines. In this study, we investigate the method of estimating the excitation force in the time domain. Tikhonov regularization and the L-curve method are employed to solve the inverse problem for the input-output relation expressed in the convolutional form and the excitation forces are estimated in time domain. When the excitation forces cannot be measured directly, the excitation force is estimated from the acceleration response of other places. Generally the excitation points and the response measurement points are different positions. However, the estimation accuracy is significantly degraded when the measurement point is near the excitation point. In this study, we prove that this reason is the effect of the direct term from the excitation force to the acceleration. The estimation results of the input-output relation reconstructed in the convolutional form are compared with ones obtained by deriving the state equation from the realization problem. We investigate the influence of the direct term on the estimation results. As an example, we perform an excitation force estimation experiment on a five-layer structure and a cantilever beam, and investigate the influence of the direct term when the measurement points of the excitation point and the acceleration response are near each other. It is found that the degradation of the estimation accuracy is small even if the response points and the excitation points are close when the direct term is considered.

This paper is concerned with the estimation of non-stationary input using Kalman filter theory. It is important to understand the excitation input for vibration control. In reality, it may be difficult to directry measure the excitation input, so we will work on the inverse problem of indirectly estimating the excitation input from the vibration response. There are two types of input estimation in the frequency domain and in the time domain. In this research, the latter method is adopted. This method has the advantage of being able to estimate nonstationary inputs compared to the another method. In this study, the impulse input is estimated as a nonstationary input. The input is estimated using an expansion system in which the input is included in the state quantity. In the simulation, the excitation input is applied to the mechanical structure with 5 degrees of freedom, and the excitation input is estimated from the vibration response. In this study, we aim to improve the accuracy of input estimation by time updating some covariance matrices which are adjustment parameters of Kalman filter.

Ring mode is considered to be correlated with the acoustic level inside a fairing of a launch vehicle. The ring mode of a simplified rocket fairing model with the ring frequency of 10.2 kHz is investigated by both of the modal analysis based on the Finite Element Method (FEM) and experimental modal analysis. The resolved frequency range in this study is set to 20 kHz. Through the experimental modal analysis, the modal damping is found to be approximately 0.05 % which is given to the Finite Element Method. Seven ring modes are clearly obtained both in the numerical and experimental results. Although the deviation of the frequency is observed about 60 to 300 Hz, reasonably agreement is obtained on the modal shapes.

Measurement of natural vibration of acoustic space is effective for noise reduction in the cabin room of vehicle (e.g. auto-mobile, railroad car and so on). In general, multi-point excitation is useful to measure natural vibration of three-dimensional acoustic space with high damping on boundary surface. However, multi-point excitation needs adjustment of amplitude and phase for each actuator. Thus, multi-point excitation is difficult to implement. In this paper, the measurement technique of natural vibrations of acoustic space by multi-point excitation using decentralized control with local feedback control is used. Local feedback control generates force in the direction of motion, which had been presented by authors. In this paper, influence of increasement of excitation point controlled by local feedback control is investigated. Firstly, decentralized control using local feedback control is introduced. Local feedback control can cancel the influence of damping in acoustic space. Thus, signal of multi-point excitation using speakers controlled by local feedback control are automatically adjusted synchronizing via natural vibration. Secondly, the problem of multi-point excitation using decentralized control is verified. It is clarified from the experiments by single-point, four-points and nine-points excitation that measurement accuracy of natural vibrations gets the influence of number of excitation points. Finally, natural vibration modes, which can not be measured by single-point and four-point excitation, can be measured by nine-point excitation.

Lawnmower is popular machine to cut grass and trimming gardens. This machine is generally driven by engine, hence lawnmower sometimes makes large vibration and has a possibility to make vibration syndrome. Thus, the vibration reduction of the handle is very important. In this study, we aimed a handle vibration reduction of a lawnmower by unbalancing a blade considering the contribution of engine vibration to the handle and the moment. Through a contribution analysis, the large engine up-down vibration was found to be the main contributor of the handle vibration, and the engine vibration was excited by the pitching moment of the blade cover. Accordingly, we attempted to reduce the pitching moment to decrease the high contribution engine up-down vibration by the blade unbalancing. As the result, the engine vibration along up-down direction could be reduce largely by adding a small weight on the blade tip. In addition the handle vibration of the lawnmower was also reduced very well by the reduction of the high contributing engine up-down vibration.

In this investigation, a numerical procedure that accounts for stick-slip phenomenon for analysis of belt slip is developed. The mechanism of the belt slip is confirmed by the physical model and the experiment. In order to model the stick-slip phenomenon between the belt and the pulley, the belt is split into the multiple elements and the fixed constraint is used for representation the stiction. If the tension applied to the belt element is smaller than static friction force, then the fixed constraint is enabled, else it is disabled and calculated under the dynamic friction. The numerical results obtained by the proposed model are compared with the measurement results for validation and that validity is confirmed.

This paper describes vibration analysis using finite element method for a flexible elastic frame with a damped panel connected by nonlinear concentrated springs under impact load. For weight saving, the frame is more flexible and mass less than the comparison frame. Finite element for the nonlinear springs are expressed and are attached to the elastic frame with the panel modeled by linear solid finite elements. A viscoelastic damping material is laminated on the steel panel. The damping layer is also modeled by solid elements in consideration of complex modulus of elasticity. The restoring force of the springs have cubic nonlinearity and linear hysteresis damping. We numerically calculated the nonlinear impact response among nonlinear springs, panels and frame structures. Using the results, we considered the influences of the weight reduction on the nonlinear vibration phenomenon.

This paper describes vibration analysis using finite element method with Model Strain Energy Method for steel panel connected by nonlinear concentrated springs under impact load. The panel is composed of steel layer having an Acoustic Black Hole with residual thickness with a viscoelastic damping layer. Finite element for the nonlinear springs with hysteresis are expressed and are connected to the panel modeled by linear solid finite elements in consideration of complex modulus of elasticity. We calculated modal loss factors and transient responses including internal resonances in the eigen modes including coupled motions between the non-linear springs and the panel. From the dominant eigen modes and the time histories, we clarified effects of an Acoustic Black Hole having residual thickness and non-linear springs on the nonlinear damped responses.

Vibration suppression is an important technology both industrially and environmentally to realize a comfort industrial product with a safe structure. In this paper, we carry out for numerical simulation of damped vibration structure having porous material sandwiched by double walls. The base plate in double walls has a Krylov type acoustic black hole. Three edges in the rectangular base plate are fixed, and one edge where the black hole exists, has free boundary. Damping material is on the surface of the black hole. Numerical analysis is performed to clarify changes of vibration reduction and vibration transmission from the base plate to the cover plate due to the acoustic black hole using FEM and MSKE method proposed by Yamaguchi et al.

In EVs and HVs that have become widespread in recent years, there is a problem that low and medium frequency noise such as wind noise and road noise is noticeable while noise caused by the engine decreases. To this problem, double wall acoustic metamaterials are highly effective. However, due to the resonance of the middle air layer and the resonator, there are frequency ranges in which the sound insulation performance degradation, this study proposes a structure in which the bottom of the resonator is thinned. By the resonance of the membrane, sound waves of opposite phase to the noise are generated, the transmitted sound waves are canceled, and extension of the functional frequency is examined.

In previous researches, acoustic metamaterial plates, in which Helmholtz resonators are periodically included in a glass plate at intervals of a wavelength or less, improve the sound transmission loss (TL) at 2.1 kHz. However, the human ear is sensitive to sounds at 2 kHz and higher, and further improvement of TL is essential. In this study, we will improve the TL at 2.1 kHz by changing the shape of the neck of the Helmholtz resonator from cylindrical to tapered. The volume of the neck of the resonator is the same as the cylindrical shape, and the length of the neck and the radius of both ends are changed. The numerical analysis using the finite element method makes a TL comparison of the resonator with a cylindrical neck and a tapered TL.

The performance enhancement of the acoustic insulation is demanded for the high frequency for interior noise of car. The importance of car comfort is emphasized, and there is also a response to the United Nations external noise regulations, and quietness is required from the design concept stage. Measures on the sound source side are also limited, and measures on the vehicle body side are important in consideration of cost and weight. In this study, we considered using the material of the new structure for the undercover of the car to improve the quietness outside the car. A simple model of metamaterial (repeated structure) is created using the finite element method, and the result of analyzing the sound absorption characteristics by numerical calculation is reported.

A topology optimization method to design micro structures of sound-absorbing poroelastic media utilizing the homogenization method based on an asymptotic expantion is proposed in this study. Design sensitivities of homoginized propoerties with respect to design variables defined on nodes of a microscopic finite element model are derived by using the homoginization method and the adjoint variable method. Then, design sensitivities of macroscopic objective function, which is dissipated power in this study, with respect to design variables defined on nodes of a microscopic finite element model are derived by using the adjoint variable method. The design variables are updated by using Method of Moving Asymptotes (MMA). Here, the design sensitivities both in microscopic and macroscopic scales are verified by a numerical examples.

Generally, a mesh cover is attached to the front of the speaker to protect the speaker. It was confirmed by an experiment that the sound pressure changes depending on the distance between the speaker and the cover, the thickness of the cover and so forth. I introduce the result that calculated this phenomenon using FE model. The influence of the cover was confirmed that below a certain frequency, the sound pressure is increased by the resonance phenomena and sound pressure is reduced by the sound insulation effect in the frequency range above that. Similar results were obtained when the thickness of the cover was changed. We also report the calculation results when the hole diameter is changed and when the distance between the cover and the air is changed.

We report the effect of acoustic transmission loss of double-walled structure including thin film cells by film height. The experiment showed that this double wall structure has higher sound insulation performance than the hollow double wall. The sound transmission loss of the high performance double wall structure with different film heights was calculated by numerical analysis using finite element method (FEM) and transfer matrix method (TMM). The rigidity of the thin film closed space structure decreased as the height increased, and the sound transmission loss increased in the high frequency region of the high film height model.

Create a microstructural model of a fiber-based sound absorbing material with a fiber diameter of 1μm or less using the finite element method, calculate the sound absorption coefficient and flow resistance by the homogenization method, and compare the results with the measured values. investigated. It is assumed that the microstructure model has a periodic microstructure, and the fiber orientation is 0°,90° using a parallel fiber model in which the fiber arrangement is uniform and a Suggard fiber model in which the fiber arrangement is shifted by half the interfiber distance. Assuming that the sound absorption coefficient and the flow resistance were calculated. From the results of sound absorption coefficient calculation, if the fiber diameter is 2μm or less, the frequency characteristics largely change depending on the fiber arrangement, and in the Suggard fiber model, the peak of the sound absorption coefficient appears smaller in frequency compared to the parallel fiber model. In the visual structure model, no significant change was found in the frequency characteristics. From the comparison of the measured values of the calculated values, the smaller the fiber diameter, the greater the divergence between the calculated frequency characteristics and the measured values. As compared with the parallel fiber model, the flow resistance of the sudgard fiber model is larger than that of the parallel fiber model. As a result of the calculated value and the measured value of flow resistance, the difference between the calculated value and the measured value was small regardless of the fiber diameter.

On mid-frequency, if you focus on the frame structure related with vibration transmission mainly, It is difficult to understand the mechanism of transmission between frame structure quantitatively and suggest the effective method to reduce vibration transmission because of the shape of wave modes at the frame structure with cross-sectional deformation. In this research, the method that is the structure change to make the transmitted wave that has the wave mode with cross-sectional deformation reflect is considered. Firstly, the hypothesis that reflection coefficients increase because of the incoincidence of wave modes can be considered. After that, it is quantitated, the idea to increase the wave reflection can be cleared by comparing with reflection coefficient. If the mechanism wave refection increases were figured out, it would be beneficial to design without calculating reflection coefficients. It is possible to calculate reflection coefficient, however, the more the number of wave modes increase, the more it becomes difficult to calculate it automatically and it costs a lot. Moreover, when the structure is changed, it is difficult to devise the structure by optimization because design conditon including strength has to be taken into account except for vibration transmission. Consequently, it would be beneficial to propose the structure at the consept design if the mechanism wave refection increases could be simplified.

Vibration reduction of vehicle is essential to improve the ride comfort. For evaluating the ride comfort, the vehicle vibration is occasionally analyzed in time domain. In this study, we propose a method to obtain the high contributing vehicle body vibration behavior deteriorating the ride comfort at a transient condition in time domain. We considered and applied two methods to realize the time domain analytical method. In the first method, we applied principal component (PC) analysis to the time domain vibration acceleration signals of the multiple body points at the transient condition to obtain the important vibration behavior. In the second method, we applied the PC analysis to the frequency domain signals and re-generated time domain signal by inverse FFT (IFFT). Through a simple vehicle vibration test at a transient condition and the comparison of the result, both methods were found to have ability to extract the high contributing body behavior at the transient condition but the second method utilizing IFFT was clarified to be more useful and accurate method.

This paper presents numerical verification of error detection method of the frequency response function (FRF) between an actual acoustic field and its finite element (FE) model. The model updating approach that uses a sensitivity of FRF and optimization algorithm has been conventionally applied for greater accuracy. Usually, a parametric design variable such as the acoustic impedance is adopted as an updating variable, which allows the calculation to be more easily generated. However, the actual error factors are included in a non-parametric case. For this reason, its application is limited. The accessible concept of utilizing the driving point FRF has often been practiced in engineering. With this technique, a driving point FRF of each point in the acoustic field is compared with an actual acoustic field and the FE model to detect the error factor. Nevertheless, it is difficult to recognize such a factor precisely. Because, the FRF is calculated from the time history, which contains reflection waves from the entire system, and the driving point FRF involves not only the participation around the excitation point but also the entire system. We therefore propose a new approach using a driving point transient response. When a certain point is excited, the sound wave propagates from the excitation point toward the whole system. A driving point transient response, which is immediately measured after excitation, includes only the participation around the excitation point. By comparing the driving point transient response with an actual acoustic field and the FE model, it is possible to clarify whether the excited segment is an error factor. In this paper, as a verification, numerical result of error detection method is shown.

This paper describes new vibration analysis methods for the coupled vibration between the acoustic field and continuous structure located inside the acoustic field. Numerical analysis methods such as the finite element method and finite-difference time-domain method have been used to analyze the coupled vibration. These numerical analysis methods need spatial discretization; however, the proposed analysis methods do not need spatial discretization because the proposed methods use the superposition of the vibration modes of the original acoustic field as a continuous body. Mathematically, the superposition of the vibration modes is a kind of series. The coupled vibration is expressed by the series of the superposition of the vibration modes in the proposed methods. Based on this concept, two methods are proposed in this paper: one is referred to as a built-in method, and the other is referred to as a binding method. The characteristics of the continuous structure is built in the acoustic field in the built-in method. In contrast, the acoustic field and the continuous structure are bound by the sufficiently stiff elastic body in the binding method. The governing equations of the analytical models were derived, and the effectiveness of the proposed method was verified through simulations.

Recently, principal component (PC) contribution analysis using operational TPA has been proposed, and it enable us to grasp the body vibration behavior of the target vehicle affecting significantly to the interior noise. However, in case the target vehicle has a frame, identifying which part between the frame and the body had better to be measured intensively to reduce the interior noise effectively is difficult. In this study, we considered a method informing us to identify the high contributing part utilizing PC contribution analysis and the original OTPA sequentially. In the test, a simple vehicle model was employed and random signal was given to the tire. The interior noise and the vibration acceleration signals at multiple points of the body and frame were recorded simultaneously. In the first analysis, the high contribution body vibration behavior to the interior noise was extracted. In the second analysis, the high contribution frame vibration to the high contributing body mode was analyzed. Through these analyses, the main factor increasing the interior noise was estimated. In addition, the countermeasure according to the estimated main factor was considered using CAE technique. As the result, the interior noise could be decreased well by applying the countermeasure to the obtained main factor.