This study investigated the noise reduction effect according to the structure of the sound-absorption and insulating materials in order to maximize the noise reduction effect in various noise environments. For this purpose, the transmission loss according to the change in hole size of the performated plate in sound-absorption and insulating board was predicted using an CAE model. The sound-absorption and insulating board was modeled and the computation of the transmission loss was performed after applying the physical properties and boundary conditions. The pure sounds of 32Hz to 4,000Hz were generated, and the analysis was performed by changing the diameter and pitch of the perforated plate. It was confirmed that the influence of the diameter and pitch of the perforated plate is closely related to the structure that make up the sound-absorption and insulating material. In order to effectively reduce the variously changing noises, it is believed that a method of improving transmission loss for each frequency band of interest is needed by changing the structure of the sound-absorption and insulating material so that the diameter and pitch of the perforated plate can be changed.

Road surfaces and tires have a great influence on road noise in automobiles. Therefore, this study attempted to investigate the effect of changes in road surface and tire tread on road noise. For six road surfaces, road noise was measured and analyzed while changing two types of tire treads. In all frequency bands, the sound pressure of the road surface with a relatively large roughness was higher than that of other roads. And in the case of a road surface with relatively large pore, it was investigated that noise was reduced compared to other road surfaces due to the sound absorption effect in the low frequency area. On roads with irregular road roughness, the high sound pressure was exhibited in all frequency bands regardless of tire tread, indicating an increase in road noise due to irregular wear on roads. It was confirmed that the noise deviation due to the change in road surface was larger than the noise deviation due to the tire structure, and it is judged that noise research according to the structure and condition of the road surface.

Speaker is the converting device which change electric energy to sound energy, and we can easily see the speaker. They are widely used to home and car audio unit, home and industrial alarm device. Sometimes, the alarm sounds cause the environmental noise. Therefore it is important to design the appropriate speaker according to the installed device and position. In order to study the vibration and sound characteristics, the curvature of the cone paper is changed. Finite element method is used to compute the vibration characteristics and mode. Indoor and Vehicle teats are carried out to investigate the non-linear characteristics and the sound characteristics for some car speakers.

Most of speakers, the con-paper (con shape) or vibration plate generate the sound by reciprocating motion which is received vibrating signal from voice coil. On the other hand, the vibration speaker that reproduces sound by attaching a vibration head to some materials such as wood, plastic, glass plate, etc. instead of cone paper or vibration plate generates different sound timbres depending on the attached materials with vibration head. so we can hear a variety of timbres than ordinary speakers. In this study, the characteristics of vibration and sound propagation according to various materials attached to the vibration head of the vibration speaker were experimentally investigated and this sound propagation characteristics were compare with woofer speaker and micro speaker. As a result of sound propagation characteristics of vibration speaker, the reproduction ability of low frequency band wes inferior to compared than woofer speaker and micro speaker. This is judged to be due to the material characteristics of glass and wood which are source of the sound propagation. As compare with 1kHz sine tone, the woofer speaker has not generated the high order harmonic component, but the glass plate and wood plate used with the vibration speaker head have generated the high order harmonic component at a level that can not be ignored. According to above results, the vibration speaker will be had a low articulation of sound because the higher volume to generate the high distortion.

In the car speaker, because the sound characteristics is changed by the space of car which mount the speaker, the speaker elements must be decide according to sound field. In this study, the nonlinear characteristics, the frequency response and the sound pressure for the same size speakers which is adapted to domestic car model are investigated. The car model is classified to semi-midsize, midsized, full size automobile in order to change the car space. As a results, we can investigate the differences of the force factor and the stiffness of suspension system for speaker. According to the change of the speaker characteristics, the sound pressure is changed, also. In the future, these data will be used to investigate the correlation between the sound quality and measurement data.

The various hydraulic equipments including main control valves are composed of relatively long replacement parts, so the stability is very important. These systems ensure system safety by not delivering pressure to actuators when pressure exceeds the limiting pressure. According to various hydraulic equipments, the required pressure of every hydraulic actuators are differenced. So the optimal design of the main valve is indeed needed. In the previous study, the detail shapes and the boundary conditions of the main control valve were studied by CFD analysis using FLUENT. Based on the previous study, the optimal design of the main control valve is done by applying the parametric modeling technique and then the optimum design of the main control valve is investigated by CFD analysis.

The air conditioner is an instrument to make a low degree fresh wind by compress a refrigerant and through the heat exchanger. As change a refrigerant of low degree and low pressure to high degree and high pressure, it is needed to the compressor. The compressor compress a refrigerant by transfer the rotational energy to reciprocating energy. The goal of this research is for easy use to failure diagnosis of an automotive compressor according to vibration characteristics of each failure types of automotive compressor. To do this, we have prepared the normal products and made some detective products which several kinds of detective types to measure and analysis of vibration characteristics. From the results, we have made a close investigation into the vibration characteristics of each kinds of detective type.

To control the flow of fluid, several kinds of valves are used. Especially, Main Control Valve (MCV) is the key element of hydraulic system which performs complex control not only controlling the flow of fluid, but also prevent damage of equipment by supplying proper hydraulic pressure to actuator and draining over-supplied hydraulic pressure. While general control valves are producing in domestically, entire quantity of main control valves are depended on importation and it depreciates competitiveness in cost, and time. In this study, to derive the best design of notch structure by following the orifice flow of 6-linked main control valve and the relation between “notch structure” which is the most fundamental element to control the velocity of the fluid and “pressure distribution”, the flow characteristic is compared by comprehending hydraulic pressure and velocity of the fluid using CFD simulation when spool valve is used for “meter-in” and “meter-out” through the opening of the notch structure.

This experimental study was conducted to identify the correlation between speaker design factors and T/S parameters. For experiments to be conducted in the study, the sample speakers modified the damper, sub-cone, and mass of diaphragm of woofer speaker for vehicles were made to find characteristics of mechanical factors of speaker and non-linear factors; and the sound pressure characteristics were investigated. The correlation between design factors and T/S parameters showed that the strength of suspension system and the mass of motor part increased with the increase of mass of cone paper; and the force factor and resonance frequency tended to exhibit different behaviors according to the changes of damper.

Various types of hydraulic valves are used to control hydraulic equipment including construction equipment such as excavator, crane. etc. The main control valve is a core component, to complex control fluid flow or supplying constant fluid pressure to actuator in accordance operating environment. Excessive flow rate is drained for safety of hydraulic system by main control valve. In this study, the scheme program to change the boundary condition according to behavior of the spool valve is developed. Using this results, the CFD analysis are accomplished.

The bending exercises of radial tire is one of the most important structural properties of the sidewall relating to ride and road noise of automobiles. The frequency band analysis is more useful for analyzing tire road noise due to property change of tread and sidewall. In this paper, the vertical stiffness and lateral stiffness of tire which have a various tread and sidewall is measured and the road noise is measured about same road condition. Furthermore, we investigated the effect on the structure of the tire tread and sidewall for the sound pressure level.

The many parts in the hydraulic equipments subject to load by hydraulic pressure. And some parts which are installed to the inside of the hydraulic equipments subject to load by the hydraulic pressure as well as the fluid speed. The inside of the valve generally generates the flow. Considering the valve expansion or the flow of the large valve, the flow is similar to the fluctuation flow in the opened flow system. In this study, the analysis of the flow including the fluctuation are performed and this results will apply to the optimal shape design of the flow path. The load acting on the structure was analysed according to the change in the shape and flow speed of the structure which install in fluid, and the safety evaluation wad investigated in consideration of the flow speed and the depth of fluid.

A deformation of tire structure cause characteristic change of tire as stiffness, ground surface shape, vibration and noise. As a result it will affect "riding quality" factors such as noise and vibration. In this study, figured it out the difference of tire pass by-noise according to ground pressure and stiffness change, to investigate the influence of tire characteristic for tire pass-by-noise. Therefore, The tire ground stiffness and tire pass-by-noise was measured according to pass-by-noise test method(ECE R117). Conclusively, “The tire pass by noise” was confirmed that between vibration and tread shoulder are a close relationship. As the tire shoulder vibration is low, “The acceleration pass-by-noise” can be seen that displayed lower value. In order to distribute contact pressure low for reduce the acceleration pass-by-noise, it could be confirmed that the shoulder stiffness should be greater.

The tires changes characteristics of the element constituting change. Stiffness is one of the various characteristics of the tire. Stiffness of the tire is change contact contour. it is known to affect vibration and noise of the vehicle. In this study we conduct to find influence of change stiffness of the tire due to vibration characteristics inside passenger car. For this study we choose tires of available on the market and measure vertical spring rate and lateral spring rate. Also through the real passenger car we find vibration characteristics in the inside of car. In conclusion, vibration energy is reducing with increase in the stiffness and we find the high vibration level of low frequency band in passenger car due to decreasing stiffness.

The hydraulic equipments has a high utilization in the many works such as the excavation, planation and crane works in the construction sites. They are an essential equipments in the construction site and the loading & unloading works of the large size objects. In the many parts which are composed of the hydraulic equipments, the main control valve(MCV) is the core of the equipments. The hydraulic energy from the pump controls the direction and the rate of flow and supply the pressure energy to the some actuators by MCV. In spite of the domestically producing of the common control valves, the MCV which used to the domestic equipments is imported the whole quantity. In this study, it is to reverse-engineer the MCV as the first step in the development of the MCV. To analyze the notch of the spool and the flow path and to apply the formula technique, we try to realize the optimal modeling of the MCV.

The improvement of car driving comfort is requested according to development of automobile manufacturing technology. Therefore, many experts have been studying automotive vibration of normally driving cars to improve automotive driving comfort. Vibration characteristics of a tire play an important role to judge a ride comfort ability and sound quality for a vehicle. A lots of study on the ride and the noise to reduce the vibration in the 20∼100Hz frequency range was being carried out for years. The tire impact due to the bump is the main factor of the vibration in the 20∼100Hz. This vibration is related to the harshness which perceive the displeasure or noise. In this study, we investigated the characteristics of the impact harshness due to the stiffness of the tire tread part according to change the tread compound.

The loudspeaker is the directly radiated speaker which generates the sound by the vibration of cone paper. Therefore the shape and the vibration characteristics of th cone paper is important factors affecting the performance of speaker. The vibration mode of cone paper is piston mode that vibrates to the up-down direction, and we can see the divided vibration in the higher mode. Because the loudspeaker has a damper, the vibration mode is different to the mode of the only cone paper. In this study, the vibration mode of cone paper which considering the damper and the effects of the damper diameter were investigated by finite element method

The characteristic test define the thiele-small parameters and the speaker is modeled to linear or non-linear model by thiele-small parameters. The performance test is carried out the sound quality by feeling test(subjective test) and objective test. The feeling test has many problems in a viewpoint of reliability, repeatability and preference that are related to judge. The study on the correlation between feeling test and objective test are carried out in some researches and introduce the loudness, sharpness, roughness and fluctuation strength. In this study, the loudness characteristics, which is related to sound quality, of the woofer speaker that are fitted to the domestic vehicle is investigated by measurement

Among many potential problems associated with automobiles, the problem regarded as most sensitive and important to the customers is the automobile’s quietness. In particular, because the trend toward the high-performance automobiles is increasing, the quietness should be considered reflecting the increasing demand of the customers for the comfort of automobile ride. Road noise is the low-frequency range in the region of 20Hz to 350Hz, generated when the tires are making contacts with the rough road surface while the automobile is running, in which the noises are resonating within the passenger compartment or with the automobile suspension. In this research, among the factors related to the road noise, the influencing factors associated with the suspension and the tire design were investigated. In particular, among the tire design factors, the structure and the rubber material were investigated as the influencing factors, and for the investigative purpose, experimental tires were manufactured and road noise evaluations were conducted thorough actual feeling tests. Then the test results and correlations were analyzed using the 6-Sigma statistical method. Results from this study shows that, among the tire design factors, the apex is the most influencing factor, in which the height of the apex is the key. The influential factors were found out to be apex height, belt angle, and tread hardness, in that order, and when the suspension is of a same kind, the tendency of the road noise was found to be similar.

In the car speaker, because the sound characteristics is changed by the space of car which mount the speaker, the speaker elements must be decide according to sound field. In this study, the mass of cone paper and damper is changed and the characteristics of the sound pressure and loudness are investigated by the experimental approach. According to the change of the speaker characteristics, the sound pressure and loudness level are changed. The effect of the con paper is larger than that of the damper in the aspect of the loudness. In the future, these data will be used to investigate the correlation between the sound quality and measurement data.