The noise of large and high-power machines was evaluated and the establishment of mitigation measures was studied. The noise level of large machinery and high-power machinery installed at domestic plant sites was investigated and compared with the noise disclosure regulations to see if they met the standards of the Occupational Safety and Health Act. This investigated the soundproofing design of large and high-power machines and the soundproofing design of complex noise of large machines installed in the plant, and prepared the design standards of the plant design company. In the future, we will compile a database of data to secure standards for research and plant design related to noise reduction, and propose noise improvement and management measures for large and high-power machines.
The tribological properties of TiC, TiN and TiC/TiN coatings on steels prepared by the cathodic-arc (CA) ion plating technique were investigated. Experiments were carried out on a tribo-test machine using a Falex journal V block system. The friction and wear characteristics of the coatings were determined by varying the applied load and sliding speed. The TiC, TiN and TiC/TiN coatings markedly increased the tribological characteristics of the surface. As far as a single layer coating was concerned, TiN goes better results than TiC. However, the TiC/TiN multilayer coating performed better than either single layer coating. The major factor in the improved performance of the multilayer coating was the role of TiC in improving the adhesion between the external TiN layer and the substrate steel.
Most domestic pilots are trained at local airfields using propeller aircraft. Training aircraft are mainly trained in the airspace around the aerodrome, and mainly take-off and landing exercises that require a lot of practice among flight control skills. Aircraft noise is a sound that humans do not want. In this study, based on the Rotax 914 engine used in Korea, the propeller blade angle was changed by 1 degree for the 3-leaf “K company” propeller and the 3-leaf GSC wooden propeller, and the engine RPM was changed to examine the noise and thrust changes. The purpose of this study is to check whether noise and thrust loss are the least at the engine's maximum RPM, and to propose an aircraft operation plan in the noisy aerodrome area based on the values.
A theoretical model has been studied to describe the sound radiation analysis for a railway under the action of harmonic moving line point forces. When a railway is analyzed, it had been modeled as curved beams with distributed springs and dash-pots that represent the radial, tangential stiffness and damping of rail, respectively. The reaction due to fluid loading on the vibratory response of the curved beam is taken into account. The curved beam is assumed to occupy the plane y=0 and to be axially infinite. The curved beam material and elastic foundation are assumed to be lossless Bernoulli-Euler beam theory including a tension force(T), damping coefficient(C) and stiffness of foundation(κ2) will be employed. The expression for sound power is integrated numerically and the results examined as a function of Mach number(M), wave-number ratio(γ) and stiffness factor(ψ).
Noise is a sound that humans do not want. In this study, noise is measured for C172, the most frequently used general aviation trainer in Korea and abroad. In addition, in this study, noise measurement points are selected for Muan Airport, where most of the domestic training aircraft fly under the supervision of the Ministry of Land, Infrastructure and Transport. Based on this, the measured data is scaled and analyzed. In addition, we intend to analyze what characteristics C172 aircraft have unique through frequency analysis of noise of C172. Through this, it is intended to understand what type of noise training aircraft affect in future studies.
Due to the development of the industry, the machinery of plant facilities becomes large and operates at high speed and high power. Workers at plant facility sites are exposed to high noise and impact noise, and the number of people with noise-induced hearing loss is increasing every year. Therefore, in order to minimize such damage, many efforts have been made to reduce the noise of large machines in production facilities. Measures, education, and recommendation of wearing hearing protectors are needed to protect the hearing of workers in high noise industries. In addition, it is urgent to reduce noise sources by blocking noise propagation paths, such as installing noise boxes and silencers, and installing facilities and equipment that generate less noise. It is necessary to repair the noise reduction device of the large machine of the plant or to study the noise reduction device when designing the plant.
Various kinds of friction materials were manufactured by adding 10%, 20%, and 30% of reduced iron, respectively, which has been obtained during the reduction process of blast furnace sludge extracted from the blast furnace, and its iron oxide, instead of existing barium sulfate(BaSO4) among the components of automobile brake friction materials. Fundamental physical property test and friction performance test, etc., using a brake dynamometer were carried out against these friction materials. Furthermore, when the expensive filling material, BaSO4 was substituted by reduced iron and added to the friction material, the added content of reduced iron for an excellent friction characteristic considering the heat emission temperature, wear, etc., was 10%. In the fundamental physical property test, as the added content of blast furnace sludge or reduced iron increased, and as the content increased, the shear strength and bonding strength of friction materials decreased, but both of them indicated sufficient strengths to be applied to a friction material. Even in the frictional performance test using a brake dynamometer, as the added content of blast furnace sludge or reduced iron increased, the friction coefficient reacted insensibly to brake deceleration, and its stability was improved.
The styling of automobile wheels and their effect on vehicle appearance has increased in importance in recent years. The wheel designer has been given the task of insuring that a wheel design meets its engineering objectives without affecting the styling theme. The wheel and tire system is considered as a vehicle component whose dynamic modal information of the tire/wheel system are employed in the modal synthesis model of the vehicle. The Modal characteristics of a Automobile wheel play an important role to judge a ride comfortability and quality for a Automobile. In this paper, the modal characteristics of a Al-alloy and steel wheel for Automobile are studied. Natural frequency, damping and mode shape are determined experimentally by frequency response function method. Results show that wheel material property, size and design are parameter for shift of natural frequency and damping.
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.
Stone cutting process that it became with the tree, after fixing with the neck which is was fixed the stone in portable type transfer and department with cutting department which is in the process of operating and it transferred it was in the process of moving with the method which cuts with hour vibration where the stone will reach to the saw blade it was caused by, the raw materials waste and the inferior good which under the actual conditions which are disconnected from the default location of the stone are caused by soaking pit of the stone were under occurring. Consequently objective of this research currently the fixation stone cutter which is used from the stone processing and cutting enterprise about lower the productivity falls on a large scale with fixation, the raw materials loss to be many is sufficient the satisfactory degree of the enterprise considerably and to be insufficient in order the problem which is like this to solve the new cutting technical develop.
A theoretical model has been studied to describe the sound radiation analysis for structure vibration noise of tire under the action of random moving line forces. When a tire is analyzed, it had been modeled as curved beams with distributed springs and dashpots that represent the radial, tangential stiffness and damping of tire, respectively. The reaction due to fluid loading on the vibratory response of the curved beam is taken into account. The curved beam is assumed to occupy the plane y=0 and to be axially infinite. The curved beam material and elastic foundation are assumed to be lossless Bernoulli-Euler beam theory including a tension force(T), damping coefficient (C) and stiffness of foundation(κ2) will be employed. The expression for sound power is integrated numerically and the results examined as a function of Mach number(M), wave-number ratio(γ) and stiffness factor(ψ). The experimental investigation for structure vibration noise of vehicle tire under the action of random moving line forces has been made. Based on the STSF(Spatial Transformation of Sound Field) techniques, the sound power and sound radiation are measured. Results strongly suggest that operation condition in the tire material properties and design factors of the tire govern the sound power and sound radiation characteristics.
Assessment of noise exposed population is to check the environment noise level and social influence in order to reduce the risks such as annoyance and disturbance that are generated by environmental noise. Also, this method suggests the preferential noise abatement policy and action plan by accurately finding the area that the noise causes harmful effect to human health. Recently, a noise map, which can predict noise in comprehensive area, is used for the assessment of noise exposed population, breaking from the methods using existing measures. In particular, countermeasure for noise can be considered more effectively by using assessment methods of noise exposed population for specific noise level, area and building types which are the main input factors in noise maps. In this study, we propose noise prediction at traffic noise due to noise map.
Aircraft noise loss in residential areas around small heliports is becoming more and more serious. Under the condition of long-term exposure to aircraft noise, it will not only cause physical and mental harm to human body, but also cause social and economic losses to the living environment around the airport. Therefore, it has been a serious contradiction factor in the community for a long time. This study points out the impact of noise caused by helicopter flying in aviation brigade of small heliport on the nearby residence area, The fixed noise monitoring system is set up to measure the aircraft noise every day. and selects the measurement site to facilitate the impact of noise caused by helicopter flight on the surrounding life.
The area around a certain airbase was affected by the noise of military helicopters, which seriously reduced the quality of the living environment in the surrounding area. In this paper, an automatic noise measurement system is set at 3 measurement points around the flight path of the 00 flight field. The fixed noise monitoring system is set up to measure the aircraft noise every day。 and selects the measurement site to facilitate the impact of noise caused by helicopter flight on the surrounding life. There is also a manual noise level measurement of the helicopter's maximum noise level for 7 days at 3 locations. Calculate the WECPNL value of 3 measuring points. Analyze the correlation between the aircraft noise evaluation unit WECPNL-Lden.
The purpose of this study was to improve the noise measurement method of noise sources and the corresponding noise reduction measures during each manufacturing process closest to the workers in the large and hige power machine. To this end, the noise generated in the large and high power machine was measured and analyzed, and the frequency characteristics of noise sources and the causes of noise were identified. The noise map was used to predict the noise reduction effect. Moreover, it is expected that this will ultimately contribute to the reduction of human risks caused by the noise of the large and high power machine.
The source of wayside noise for the train are the aerodynamic noise, wheel/rail noise, and power unit noise. The major source of railway noise is the wheel/rail noise caused by the interaction between the wheels and rails. The Structure borne noise is mainly a low frequency problem. The train noise and vibration nearby the elevated railway make one specific issue. The microphone array method is used to search sound radiation characteristics of elevated structure to predict the noise propagation from an elevated railway. In this paper, the train noise and structure borne noise by train are measured. From the results, we investigated the effect on the sound absorption tunnel for elevated railway.
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.