• Journal of the Korean Society of Safety
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• v.31 no.2
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• pp.90-97
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• 2016

The objective of this study is to evaluate the operator's safety for the risk assessment method of impulsive noise division. Literature reviews on the basis of the impulsive noise study, the measuring methods and procedures, based on the results of the analysis process presents a risk assessment methods. In this study, analysis of the MIL-STD-1474D, B-duration graph for the peak noise level to cross the line from the measurement results is limited by the risk retracted. It is possible to determine whether there is quick can be determined whether the risk. Measurement positions measured by the microphone is installed on the risk of applying results are so located within the tolerance impulsive noise in the measurement position can interpret subjective safety is ensured. In addition, Proportional Dose technology was the proposed by the Patterson with the risk assessment method was applied to the indoor-impulsive noise. As results of this study, results for the same value of applying the technique of Proportional Dose technology results calculated by MIL-STD-1474D methods allows 1 count once increased in comparison to the result obtained.

• Journal of Biomedical Engineering Research
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• v.31 no.2
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• pp.170-175
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• 2010

A method of measuring heart rate using photoplethysmograph(PPG) signal during exercise is proposed. PPG's are composed of strong base tones and their harmonics, and the strong base tones are trackable by the adaptive notch filter (ANF) which adjusts its coefficients to minimize the output power. The proposed heart rate measurement algorithm continuously notches the frequency component with the maximum power in the measured PPG, so that the fundamental frequency corresponding to heart rate is traced. We also presents methods of detecting degeneration and impulsive noise blocks to minimize the coefficient fluctuation. Experiments were conducted using real PPG signals captured during exercise. Results showed that the proposed algorithm is capable of consistently tracking the heart rate embedded in the noisy PPG's.

• Journal of the Korea Society of Computer and Information
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• v.19 no.6
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• pp.93-100
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• 2014

The objective of this study is to propose the measurement system implementation method for the evaluation and measurement of the indoor-impulsive over 170 dB noise source. For the purpose of measuring impulse noise, design and implementation constructed followed subsystems of the testing center, microphone, ear simulator, head and torso simulator and so on. Measurement systems for the accuracy and reliability of impulse noise are implemented when measuring 3 ways of measurements method by the simultaneous measurement system design. For the accuracy and reliability of three mutually indoor-impulse noise measurements were compared, three kinds of measuring methods in accordance with the peak sound pressure level and octave band. Comparing the results of data, the indoor-impulse noise by analyzing a frequency characteristic was validated in difference for the statistical significance. Result are determined by the influence of the reflected wave. Therefore, the flexible size of the interior test site while interior impulse noise measurement system was constructed. Throughout this system can be affected by parameters that are the impulse noise source and the corresponding frequency-characteristic analysis to determine the spectrum of the reflected wave. And, in the near future, indoor impulse noise measurement systems for acquisition and analysis are utilized in useful data.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.11
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• pp.1295-1303
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• 2010

In this paper, an effective method has been proposed for selection of white Gaussian noise(WGN) band for radio background noise measurement system under broad band noise environment. MMN which comes from industrial devices and equipment mostly happens in the shape of broad band noise mostly like impulsive noise and this is the main reason for increasing level in the present radio noise measurements. The existing method based on singular value decomposition has weak point that it cannot give good performance for the broad band signal because it uses signal's white property. The proposed method overcomes such a weakness of singular value decomposition based method by using signal's Gaussian property based method in parallel. Moreover, this proposed method hires a modelling based method which uses parameter estimation algorithm like maximum likelihood estimation(MLE) and gives more accurate result than the method using amplitude probability distribution(APD) graph. Experiment results under the natural environment has done to verify feasibility of the proposed method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.1162-1167
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• 2001

Suction valve fluttering is generated by reciprocating motions of the piston inhaling and discharging process of gas in the hermetic compressor. A reactive type suction muffler, which produces high pressure-drop because of its complicated flow path, controls the impulsive noise radiated from the flutter of suction valve. The high-pressure drop in the muffler increases the transmission loss, but reduces the EER(Energy Efficiency Ratio) of the compressor. We consider how to design the high acoustic attenuation and low pressure-drop performance to take account of the acoustic and flow performances of the suction muffler. In this study, we identified the suction noise source of compressor from the measurement of the acoustic pulsation and flutter of suction valve. We analyzed the acoustic characteristics of muffler using the finite element method, and compared the experimental and analytical characteristics of flow path of suction muffler. Theoretical predictions and experimental results are compared from the viewpoint of the acoustic performance and energy efficiency of the compressor.

• The Journal of the Acoustical Society of Korea
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• v.37 no.5
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• pp.349-355
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• 2018

A large number of parameters have been defined in order to describe and to evaluate the acoustical propeTies in rooms. Reverberation time is an impoTant characteristic of conceT halls, theaters and studios, etc. Over the years, a number of different methods for measuring the reverberation time have been developed, the most common being: the interrupted noise method, the integrated impulse response method, and the method of recording the room response to an impulsive source. However, the reverberation time can be changed by the measurement method, sound source and microphone. Therefore, it is difficult to accurately measure the reverberation time in a room. In this paper, it will be analyzed the interpretation method of the reverberation time and discussed the limitations.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.2
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• pp.249-260
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• 2014

When a train enters the tunnel at high speed, the pressure wave occurs. When this pressure wave reaches at the exit of tunnel, some are either emitted to the outside or reflected in tunnel by the form of expansion wave. The wave emitted to the outside forms the impulsive pressure wave. This wave is called 'Micro Pressure Wave'. The micro pressure wave generates noise and vibration around a exit portal of tunnel. When it becomes worse, it causes anxiety for residents and damage to windows. Thus, it requires a counterplan and prediction about the micro pressure wave for high speed railway construction. In this paper, the effects of train head nose and tunnel portal shape were investigated by model test, measurement for the micro pressure wave at the operating tunnel as well as numerical analysis for the gradient of pressure wave in the tunnel. As results, a method for predicting the intensity of the micro pressure wave is suggested and then the intensity of the micro pressure wave is analyzed by the tunnel length and the cross-sectional area.