• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.852-855
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• 2004

This experimental study describes the propagation characteristics of the impulse noise emitted from the exit of a straight pipe attached to the open end of a simple shock tube. The sound pressure level and directivity of the impulse noise propagating from the exit of pipe with several different diameters are measured in the far sound fold for the range of the incident shock wave Mach number between 1.07 and 1.26. The experimental results showed that the peak values of impulse noises had a strong dependance on the exit diameter of a pipe and the shock wave Mach number. The impulse noise had the directivity propagating toward to the pipe axis and the characteristics of inverse square law of propagation distance. Moreover, it was shown that the one-third octave band SPL of impulse noise was almost constant regardless of the frequency band.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.24 no.1
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• pp.74-78
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• 2014

Objectives: Purpose of this study was to evaluate the noise level exposures at the different cannonball type and locations in the tank gun drill ranges. Methods: We visited the tank gun drill ranges and measured with a sound level meter(3M Quest SoundPro$^{TM}$) with the value of Peak(dB(A)). Results: The highest peak value of impulse noise level averaged 166.3 dB(A) at the site of loading solider. The highest peak value of impulse noise level by size of cannonball averaged 165.9 dB(A) at the 120 mm size cannonball of the tank. This result was significantly different from the other size of cannonballs such as 7.62 mm, 90 mm, and 105 mm(p < 0.001). Among the four types of soldier site on the tank, average noise levels of loading soldier, 156.6 dB(A), were higher than the other three types of soldier site (p > 0.05). Conclusions: This study confirmed that there were needed for a proper control to reduce the amount of impulse noise exposure at the tank gun drill ranges.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.23 no.3
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• pp.261-265
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• 2013

The purpose of this study was to evaluate noise level exposures at different locations such as the left and right ears of the shooter, control room, waiting soldier location and drill ground. For this study, we visited two military rifle ranges and took measurements with a sound level meter (3M Quest SoundPro TM) at five different locations with values of Peak (dB(A)) and Max (dB(A)). The highest peak value of impulse noise level averaged 150.4 dB(A), ranging from 149.6 to 150.5 dB(A) at both the left and right ear sides. This result was significantly different between both left and right ear side locations and at other locations such as the control room, waiting soldier location, and drill ground (P < 0.001). Frequency of impulse noise exposure level showed that the left ear of shooter had the highest frequency (20 times) at over 150 dB(A). This study confirmed that there is a need for proper controls to reduce the amount of impulse noise exposure at military rifle ranges.

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1383-1391
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• 2018

A new nonlinear filtering algorithm for effectively denoising images corrupted by the random-valued impulse noise, called dual sliding statistics switching median (DSSSM) filter is presented in this paper. The proposed DSSSM filter is made up of two subunits; i.e. Impulse noise detection and noise filtering. Initially, the impulse noise detection stage of DSSSM algorithm begins by processing the statistics of a localized detection window in sorted order and non-sorted order, simultaneously. Next, the median of absolute difference (MAD) obtained from both sorted statistics and non-sorted statistics will be further processed in order to classify any possible noise pixels. Subsequently, the filtering stage will replace the detected noise pixels with the estimated median value of the surrounding pixels. In addition, fuzzy based local information is used in the filtering stage to help the filter preserves the edges and details. Extensive simulations results conducted on gray scale images indicate that the DSSSM filter performs significantly better than a number of well-known impulse noise filters existing in literature in terms of noise suppression and detail preservation; with as much as 30% impulse noise corruption rate. Finally, this DSSSM filter is algorithmically simple and suitable to be implemented for electronic imaging products.

• Journal of Environmental Health Sciences
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• v.39 no.4
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• pp.354-359
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• 2013

Objectives: The purpose of this study was to investigate exposure levels to K2 rifle noise at a military rifle range among soldiers in training, the left and right ears of shooters, and control managers in the day and night times. Methods: For this study, we visited military rifle ranges and measured the noise of a K2 rifle with a sound level meter (3M Quest SoundPro$^{TM}$) at four different locations with values of Peak (dB(A)) and Max (dB(A)). Results: The highest peak value of impulse noise level averaged 150.4 dB(A), ranging from 149.7 to 150.5 dB(A) at the left-ear side. Impulse noise levels in the daytime were also recorded as higher than during the night. This result was significantly different between daytime and nighttime locations, such as soldier training, right ear of shooter, and control manager (P < 0.001). Conclusion: This study confirmed that there is a need for proper management of impulse noise at military rifle ranges.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.71-74
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• 2005

This experimental study describes the propagation characteristics and reduction of impulse noises emitted from a high voltage COS(Cut Out Switch) fuse of a transformer. When a high voltage COS fuse becomes a short circuit by the over current. The peak sound Pressure above 150dB(A) is generated. In this study, an impulse noise generator is designed for generating the impulse noises similar to the noise level of COS fuse, which is utilized to test the noise reduction of a reactive silencer. The reactive silencers have been tested for 10 different types with each different porosity, hole diameter and length. From the experimental results, it is found that the reactive silencer has an excellent performance to greatly suppress the impulse noise and that its performance is closely connected with the porosity and hole diameter.

• Proceedings of the KIEE Conference
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• 1995.07b
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• pp.904-906
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• 1995

Based on the detection of the size of datas of multipath channel characterization, we propose a new algorithm. called the impulse size based adaptive median filter(ISMF), for ghost cancellation system. The ISMF consists of two levels. The first one is the impulse noise size detection level and the second one is the adaptive median filtering level to remove the impulse noise detected. Test results confirm that the proposed ISMF removes impulse noise due to multipath channel characterization while preserving signal as well as ghosts so that the LMS algorithm performs effectively.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.258-261
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• 2006

This study introduces the control of duration time of impulse noises emitted from a high voltage COS fuse of a transformer. When a high voltage COS fuse becomes a short circuit by the over current, the peak sound pressure level over 150 dB(A) is generated at the distance of 2m from a COS Fuse. For the purpose of the reduction of impulse noise, in this study, the reactive type silencer has been utilized. And also electrical interrupting test was experimented. From the experimental results, the reactive type silencer has been shown to have the noise reduction of about 13 dB(A). It has been found that the electrical interception performance of the COS fuse was related to the control of the duration time of impulse noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.951-954
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• 2006

This Study introduces the design of a reactive type silencer for reducing impulse noises emitted from a high voltage COS fuse of a transformer. When a high voltage COS fuse becomes a short circuit by the over current, the peak sound pressure level above 150dB(A) is generated at the distance of 2m from a COS Fuse. For the purpose of the reduction of impulse noise, in this study. the reactive type silencers have been utilized. The performance of noise reduction for them can be expressed by insertion loss. The reactive silencers have been tested for 23 different types with each different porosity, hole diameter and depth. From the experimental results, it is found that the reactive silencer has an excellent performance to greatly suppress the impulse noise. The one-stage, two-stage and three-stage reactive type silencers have been shown to have the insertion losses of about from 35dB (A) to 25dB(A).

• Journal of the Korean Society for Precision Engineering
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• v.20 no.9
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• pp.151-158
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• 2003

The impulse noise of bullet after shooting in small arms has an effect on the hearing ability of human. Although a silencer has been developed for noise reduction in small arms, there is only a few researches about relationships between the sound pressure level and the auditory sense of human. In this study, the quantitative sound pressure levels are revealed by experimental measurements of impulse noise with each silencer type. And the performance evaluation for noise suppression of a silencer in small arms is carried out to reduce a serious loss of the hearing ability of the small arms user. It is concluded that the evaluated results can be utilized for checking sound pressure and data accumulation for new small arms design with silencer.