• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1060-1065
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• 2007

This paper summarizes a design procedure of radiated noise from engine blocks of marine engines. This air-borne noise is one of the significant noise contributors including the aeroacoustic noise due to intake and exhaust and the re-radiation due to structure-borne noise. Excitation forces by engine operations are evaluated taking into account the power generation mechanism from the burning process to the subsequence motion of internal parts; piston, connecting rod, and crank shaft. The acoustic transfer vector method is incorporated to effectively simulate the radiated noise field under the various operation conditions. A contribution analysis for the various excitations to the radiated noise is conducted. It is found that the firing pressure is the main source of the radiated noise, and so the structure of the cylinder can be modified to significantly reduce the radiated noise from the engine block.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.789-792
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• 2005

The dominant noise sources of Diesel Multiple Units are powerpack, which is composed of engine, transmission and cooling system, noise and wheel-rail rolling noise. The interior noise of a running vehicle is determined by structure-borne noise and air-borne noise from these noise sources. The contributions of interior noise from each noise source are calculated by air-borne transfer functions and structure-borne transfer functions of noise sources. In this paper, source separation technique is proposed to determine these transfer functions from the results of stationary and running tests of existing vehicle. With this technique, it is possible to get hold of contributions of interior noise from .noise sources of running vehicle. This source separation technique makes it possible to take efficient measures for reduction of interior noise at the early car-development stage.

• Korean Circulation Journal
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• v.54 no.3
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• pp.140-153
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• 2024

Background and Objectives: Although a single-lead electrocardiogram (ECG) patch may provide advantages for detecting arrhythmias in outpatient settings owing to user convenience, its comparative effectiveness for real-time telemonitoring in inpatient settings remains unclear. We aimed to compare a novel telemonitoring system using a single-lead ECG patch with a conventional telemonitoring system in an inpatient setting. Methods: This was a single-center, prospective cohort study. Patients admitted to the cardiology unit for arrhythmia treatment who required a wireless ECG telemonitoring system were enrolled. A single-lead ECG patch and conventional telemetry were applied simultaneously in hospitalized patients for over 24 hours for real-time telemonitoring. The basic ECG parameters, arrhythmia episodes, and signal loss or noise were compared between the 2 systems. Results: Eighty participants (mean age 62±10 years, 76.3% male) were enrolled. The three most common indications for ECG telemonitoring were atrial fibrillation (66.3%), sick sinus syndrome (12.5%), and atrioventricular block (10.0%). The intra-class correlation coefficients for detecting the number of total beats, atrial and ventricular premature complexes, maximal, average, and minimal heart rates, and pauses were all over 0.9 with p values for reliability <0.001. Compared to a conventional system, a novel system demonstrated significantly lower signal noise (median 0.3% [0.1-1.6%] vs. 2.4% [1.4-3.7%], p<0.001) and fewer episodes of signal loss (median 22 [2-53] vs. 64 [22-112] episodes, p=0.002). Conclusions: The novel telemonitoring system using a single-lead ECG patch offers performance comparable to that of a conventional system while significantly reducing signal loss and noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.701-703
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• 2014

The intense noise generated by military aircraft hans a significant impact on ground crews and their families on airbase. For minimizing the impact of the aircraft noise on the airport, appropriate indoor noise standard is required. This paper studied to establish the indoor noise standard on the military airport. The aircraft noise was measured and analyzed the frequence characteristics. the remodeling of office for the noise mitigation was enforced to verify the appropriate internal noise standard and to select the method of reinforcement. The noise standard was classified three categories according to the dwelling, office and usage of building with flight train facilities and banishment in military airfield.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.8
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• pp.787-794
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• 2010

Recently, with sudden increase of supplying rate of cars and quantity of goods transported, traffic noisy becomes one of important factors obstruct environment of exhibition and view facilities have purpose in calmness and unsatisfaction about this is high now. Therefore, in case of exhibition and view facilities, it has to be grasped that satisfaction degree about the noisy in and out of the exhibition room by performing effect valuation on traffic noisy from design step. However the level of internal noise cannot be measured at the design phrase of the structure due to the noise of traffic. Up until now a walls transmission loss, based on the law of mass, is predicted using this method. However measuring the internal sound level after actual construction reveals that there is a large difference from measurements made at the design stage, and it is very difficult to find a solution after the opening of the structure. From research looking from this perspective the internal sound level was predicted- calculating the internal sound absorption ability, using acoustic simulation and loss prevention of an insulated wall- based on data collected to evaluate the internal sound of an exhibition room at a Folk Museum adjacent to a freeway. The results of this research are considered to provide important data for the prediction of internal sound level at the time of construction of exhibition facilities similar to this.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.4
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• pp.723-729
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• 2013

The contraction and expansion noise of a refrigerator are investigated, and some effective methods are proposed to reduce the level and occurrence frequency of noise. First, the noise of a refrigerator is measured to estimate the frequency spectrum and occurrence frequency of noise. Second, a sound visualization was conducted using an acoustic camera to determine the location of the noise source. From the results, it was observed that the internal part mainly producing noise was the third shelf in the freezer room. A method to estimate the acceleration on the location of the noise source is introduced to analyze the contraction and expansion noise precisely and accommodate experimental convenience. Noise reduction methods such as the replacement of the existing shelf with glass shelves, adoption of rail slides, and increase of roughness on the contact surface of the shelf are proposed and tested.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.4
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• pp.728-732
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• 2010

GIS(Gas insulated switching gear) is power equipment with excellent dielectric strength and is economy merit in high confidence and stability. Recently, because equipment of GIS was occurring problem of confidence used for a long time, partial discharge on-line diagnosis systems have been importantly recognized. Partial discharge (PD) detection is an effective means for monitoring and evaluation of dielectric condition of gas insulated system (GIS). The ultra-high-frequency (UHF) PD detection technique can detect and locate the PD sources inside GIS by detecting electromagnetic wave emitted from PD source. Therefore, real-time diagnostic system using UHF detection method has been developed for this application is being expanded gradually. However, the signal of partial discharge occurring in SF6 gas is very weak and susceptible to external noises which mainly consist of PD in air. Thus, it is important to distinguish the PD in SF6 gas more sensitively from the external noises. Unfortunately, these external noise signals and the partial discharge signals have very similar characteristics. Therefore, to solve this problem, we need the signal processing method for distinguish partial discharge signals with external noise signals for improvement of SNR(signal to noise ratio) and sensitivity. In this paper, we proposed internal signal processing method for removing external noise signals with built-in pre.amplifier and frequency conversion circuit.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.12
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• pp.1032-1040
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• 2001

In order to apply the partial discharge measuring technique utilizing electrical pulse to the transformer at sites, this paper describes the measuring technique obtaining only the signals due to internal partial discharge in the transformer, but the noises due to external corona which has been a major problem so far. At first, partial discharge and corona noise were simultaneously generated in the model transformer by using needle-plane electrodes and rod-sphere electrodes out of it in a high voltage laboratory, respectively. It was verified that only the partial discharge signals in the transformer could be measured by removing the noise signals from the superposed signals of partial discharges and noises on the grounding wire of the model transformer. By application to a 345kV transformer in service, it was also confirmed that the partial discharge could be on-line monitored by removing the noise signals measured by the inductance sensor on the grounding wire of a 154kV lightning arrester from the superposed signals of internal partial discharge and external corona noise measured by bushing tap coupler of the transformer.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 1996.11a
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• pp.95-101
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• 1996

The purpose of this study is to research the residents' subjective opinion the apartment noise. To attain this purpose. we investigated 182 residents' responses at “Da” apartment in Chonju. . Analysis showed the following results. The residents which are living in the building next to the road strongly felt the external traffic noise. The residents living on the first to fifth above the sixth to fifteenth also are suffering from the internal noise. Generally speaking. the apartment residents' life are considerably disturbing with noises. Especially this disturbance was serious in summer.

• Proceedings of the KSR Conference
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• 1998.11a
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• pp.388-397
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• 1998

This paper gives the way of analyzing internal noise of rolling stocks which is urgently required by civilians. Triangular beam method among ray tracing techniques is utilized to compute noise distribution of rolling stocks. Noise source and transmisstion loss of several sections from experimental work are included in this calculation. Ray tracing technique is found useful to compute big structures like rolling stocks.