In the research of the tone quality of a classic guitar, the control of the mode of vibration in the face sheet is important. It is necessary to unite traditional trial and error approaches concerning the engineering approach. Several kinds of researches for futtock layout for reinforcement in sound board of guitar here. To bring rich tone quality, we try the guitar by a technological idea like the mode of vibration etc. And, it contributes to efficient production.

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This paper clarified the excitation mechanism of picking the strings of a guitar. The picking excites forced vibration and free vibration of the strings by giving the strings impact force, friction force and initial condition. At first, separate influence of these force and initial condition was experimentally examined. Then, generation mechanism of transient responses of the strings was examined for ordinary picking technique, by the viewpoint of the influence of impact force, friction force and initial condition.

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Sound quality of impact sound becomes important in design of golf club. In this paper, two simple experiment models produced to examine the vibrational characteristic of the golf clubs. First, the results of the numerical analysis of the models and the results of the experiment are compared, and the effectiveness of the numerical model is shown. Then, confirmed the effectiveness of the proposed method for estimating impact force. Finally, it is examined the influence that a structural change in the golf clubs give to the sound quality of the impact sound is predictable by use three sound quality parameters.

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Recently, significance of human-machine interface by voice recognition techniques has been increased. Actually those techniques have been adapted to robots, ubiquitous system, cellular phone, auto-translation system and so on. Recognition researches of meaning ingredient included in human voice have been carried out mainly. However, there are many problems about the specification of speaker. The former recognition methods such as STFT, FFT, LPC and cepstrum analysis have many problems on recognizing accurately meaning, speaker characteristics and emotion state of speaker because human voice is a transient signal. Therefore, this study adopts the Wavelet analysis, which has been using widely to analyze transient signals on Time-Frequency domain. This study reveals that the level-1 detail ingredient from human voice by the discrete Wavelet analysis has some individual difference and the individuality for voiceless consonant /p/ can be identified by continuous Wavelet analysis.

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This paper describes guideline of accuracy improvement in inverse-acoustic analysis (IAA). IAA is a technique for identifying the vibration with a high contribution of the sound radiation. However, the identification result has the possibility that the result of good accuracy is not obtained. One reason is the shape of measurement points of the acoustic pressure decreases the result of accuracy. Therefore, this study focused on the shape of measurement points of the acoustic pressure. To reveal influences of shape of measurement points in identification, sound source is identified from the measured sound pressure with different shape of measurement points.

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We researched acoustic analysis on the condition that medium has flow. Simulated by using CIP(Constrained Interpolation Profile) method. We used a flat pulse and a sphere pulse. About flat pulse, we observed the sound pressure. But about sphere wave, it is difficult to search a feature from sound pressure. So we observed the transfer function. We applied uniform flow and Hagen-Poiseuille flow. Hagen-Poiseuille flow is the form in circular tube flow, so we applied circular tube boundary condition. The way is Arbitrary Oblique Reflection Boundary.

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A numerical method is proposed to calculate damping properties for mixed structure including elastic body, viscoelastic body and porous body using FEM. Displacement vectors as common unknown variable are solved under coupled condition. Besides, 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 for some automotive body panels with multi-layered sound proof structure. Vibration isolation characteristics of triple walls with sound absorbing material are compared with those of double walls with sound absorbing material.

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This paper presents a new structural design concept where the structural intensity (SI) technique is used to reduce the sound radiated from a compound plate structure. This concept is based on the modal expansion of the SI which can be classified into two types of power flow: vortex-type and straight-type distributions. Vortex-type SI would be useful for interrupting power transmission between plate subsystems of compound plate structures. On the other hand, straight-type SI would be useful for promoting the power transmission. In this study, numerical simulations are carried out to demonstrate the effectiveness (or the validation) of the concept by using J-shaped structure.

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This paper describes the damping loss factor estimation method of the statistical energy analysis (SEA) using the Power Injection Method (PIM). The parameter called loss factor in SEA is estimated by PIM. However, PIM is necessary to measure the vibration in a lot of points. Moreover, if the structure of subsystem is changed, the parameter needs to be estimated again. In this study, the influence that the difference of measurement points gave the analytical result was verified. Furthermore, we proposed the estimation method of damping loss factor on subsystem which was fitted rubber by using experimental results of attached element.

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This paper presents a new method for controlling vibration energy flow for noise reduction. The method determines the excitation location for desired energy flow pattern based on modal expansions of structural intensity. In this paper, firstly, we show the modal expansion of structural intensity for flexural vibration on flat plates. Next, numerical simulations on a flat panel by using the modal expansion of structural intensity, we propose a method for determining excition location which excite the modal components of vortex-typed and straight-typed structural intensity pattern. The numerical application results demonstrate the validity of the method.

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The applications of acoustic insulations for reduction of automobile interior noise have been researched. This paper introduces a sound pressure prediction technique using Statistical Energy Analysis (SEA) in order to reduce weight of acoustic insulations. The analytical SEA model was created, experimental SEA was conducted, and the SEA parameter was tuned up. As a result of chassis dynamo test, the validity of SEA modeling was shown, and utility of the method was confirmed. Without increasing the sound pressure level, the reduction of weight of acoustic insulations was possible.

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This paper considers an analytical and experimental investigation into the coupling problems and the active controls of acoustic power mode in the double-wall structure coupled to an acoustic enclosure. Harmonic sound plane wave from outward is transmitted into the enclosure. The purpose of this investigation is to control the potential energy in the enclosure. In the high frequency range, the acoustic sound transmitted through the double-wall structure is very low. It becomes a broadband control system by applying active control that is more effective in the low frequency range to the double-wall cavity.

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We suggest the new method of oblique-incident sound absorption measurement by the ultrasonic waves. This method can be used also to measure the random and normal incident sound absorption. The area of the specimen may be very small. The oblique-incident sound characteristics of Helmholtz reactive type resonator depends on sound incident angle. The resonance frequency shifts high as the angle of incident sound shifts from normal. However the sound characteristics of resonator with inner porous core hardly depend on incident angle.

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This paper considers active control of the sound transmission loss of a flexible panel partitioning an open space. A control strategy presented in the work comprises both active and passive control for the purpose of minimizing the total acoustic power transmitted from a panel excited acoustically from the other side, hence hybrid control. First, the sound field system produced by a double-leaf wall with air space acoustically excited is described. Cluster control is then employed, the system state being expressed. Moreover, the optimal control law for minimizing the total acoustic power is derived. Finally, both of a numerical analysis and an experiment are conducted, clarifying the control performance.

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Two cavities connected by an elastic plate with small holes are often observed around us. In the previous studies, however, the elastic plate was analyzed as a rigid one. The vibration of the plate is expected to affect sound pressure, damping and sound absorption rate in the two cavities. In this study, a structural-acoustic coupling analysis is carried out for the two cavities coupled by an elastic plate with a small hole to demonstrate the effects on the sound properties. Furthermore, the validity of the analytical model is verified by comparing the calculated results with the experimental ones.

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Vibroacoustic coupling phenomena occur in a variety of different situations and are generally studied with the goal of controlling noise. We consider a cylindrical structure with thin plates at both ends and investigate the coupling between the plate vibrations and the internal sound field when external periodic forces are applied to respective end plates. In comparison between characteristics of the both systems, it is clarified that vibroacoustic coupling is effective in increasing acoustic energy and the phase difference depends greatly on the acoustic mode, which contributes the formation of the sound field.

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The purpose of this study is about noise reduction by Active Noise Control (ANC) at the opening with a louver which attached Piezoelectric Card Speaker. In a house and an apartment not only machinery, louvers are used at large opening aimed for air conditioning and ventilation. Leakage of a sound from the opening set louver becomes a problem. In this experimental study, proposed ANC system is independent parallel control system using two single channel ANC systems. One of them, secondary noise source is set at each bane down side of louver. The other one is set slit of enclosure opening. The experimental results show that noise reduction is obtained from 5dB to 25dB in sound field on this proposed ANC system.

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In recent years, with the rise of interest in environmental problems, noise reduction of motors is required. There are three kinds of motor acoustic noise: ventilation noise, electromagnetic noise and machine noise. Ventilation noise may be assumed to commonly consists of fan noise in high speed machines. Fan noise is produced by the number of rotations and the number of fan blades and by the turbulence sound produced by the disturbed flow of cooling air. Regarding fan blade sound and turbulence sound, many studies on noise reduction have been done by flow analysis using examination of fan blade number and shape. However, papers describing the space resonance frequency of the fan space that is a propagation channel of the fan noise have not been found. Therefore, this paper describes space resonance frequencies and resonance mode of the fan channel analyzed by FEM and experiments. The effect of rotational sound and resonance mode on noise is described.

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As a sound source locali7ation method, the Acoustic Intensity (AI) method is widely used. On the other hand, the Nearfield Acoustic Holography (NAH) Method has not spread to use in industry, because this method has difficulty in measurement and analysis. However, the accuracy of this method is better than that of the AI method. In this paper, the result of the experiment by the NAH method is shown. The experiments are performed to a geared motor, and the sound source locations are examined.

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Increasing interest in environmental matters, a quiet motor are drastically demanded lately. Among of acoustic noise of the motor, electromagnetic acoustic noise is jarring and is studied recently. In order to reduce electromagnetic acoustic noise, it is necessary to design the motor, of which natural frequencies does not coincide with electromagnetic force frequencies. In order to avoid the resonance of the natural frequencies of the core and the electromagnetic force frequencies at designing phase, machine designer has to accurately predict these frequencies. In order to reduce the electromagnetic acoustic noise, this paper studies the following things, which are not clarified in previous research. Simulation method s of the natural frequency in rotor.

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Helmholtz resonator is one of the noise reduction methods. It is useful when the noise has a dominant frequency. In this study, noise reduction with Helmholtz resonator is applied to a vacuum cleaner. Through vibration tests of the vacuum cleaner, it is found that a motor is the main cause of the noise of the vacuum cleaner. In order to confirm the effect of Helmholtz resonator, an acoustic tube model is analyzed by using FEM solution and experimental approach. By evaluating FRFs of the acoustic tube model with and without Helmholtz resonator, noise reduction is confirmed. By attaching Helmholtz resonators nearby the motor of the vacuum cleaner, it is shown experimentally that the noise is reduced as expected.

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A chain drive unit is an indispensable machine element in order to perform powerful and efficient action. It is used in various places of a world. However, in high-speed transmission like a motorcycle, there is a fault that a considerable vibration and noise generate. So, it aims at low noise-ization of the chain drive unit of a motorcycle in this research. If noise can be reduced, a chain drive unit will become a perfect transmission machine element. It thought that the noise problem that is an environmental problem was also solved. In the present day when traffic relations progressed, the bad influence that it has on the human body by the noise of a car and a motorcycle is so serious that it becomes an environmental problem. Therefore, it two aims at solutions of the improvement of the fault of a chain drive unit, and a noise problem. Low noise-ization of the chain drive unit of a motorcycle is aimed.

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This paper describes vibration analysis of a tire on the static and operational condition. At first, the surface vibration velocities were measured on the operational condition to comprehend the vibration behavior of a rolling tire using the scanning Laser Doppler Vibrometers. Secondly, the tire vibration model based on the cylindrical shell theory was build up. The basic equation, including the effects of the initial tension and the Coriolis force due to rotation, was derived by thin rotating cylindrical shell model and Hamilton principal. The results of the experiment and the theoretical analysis for a rolling tire were presented.

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Spindle force is a critical factor in structure borne noise for vehicle interior noise. To research the vibration characteristic of rolling tire is essential for prediction of spindle force. There is a characteristic that 1^<st> natural frequencies in operational condition are lower than in static condition. Therefore, the consideration of the degradation of natural frequencies is necessary in the tire model. This paper describes identification method of tire equivalent stiffness In operational condition. And we propose natural frequency estimation of rolling tire from excitation tests at contact area.

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