• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3197-3202
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• 2013

When car builder designs the large carbody structure of railway vehicles, it is necessary to optimize the damping characteristics through the analysis of structure borne noise such as sound pressure level(SPL). This paper is a study on the structure borne noise analysis by characterizing the damping of double skin aluminum extruded panels for rolling stock carbody. The normalized SPL was calculated based on the simple source theory using measured mechanical mobility parameters from vibration tests(i.e. point, transfer and modal mobility). The reduced SPL was predicted by using finite element method by applying loss factor of damping material into laminated shell elements. It was found out that the damping material coated on the panels like underframe, which part is seriously affected by vibration during train run, took effect to reduce noise level.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8140-8146
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• 2015

The objective of this study is to experimentally investigate the cooling performance characteristics with the consideration of the temperature variations of the enclosure of the 400W ferrofluid active speaker having both woofer and amplifier heat sinks. In order to do this, the heat sinks for both woofer and amplifier was designed ant applied to 400W ferrofluid active speaker. As a result, the cooling performance of the developed 400W ferrofluid active speaker was improved and the temperature of the enclosure after 120 min at steady state increased by $2.8^{\circ}C$ with the increase of the outdoor temperatures from $25^{\circ}C$ to $29^{\circ}C$. In addition, the overall sound pressure level of the developed 400W ferrofluid active speaker showed 111.8 dB and improved 1.9 dB higher than 109.9 dB of the existed speaker.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.4
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• pp.285-289
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• 1997

A Held experiment was carried out to confirm the effect of underwater sound on the luring of fish school of rudder fish in a set net at the coast of Cheju Island. The effects of the acoustic emission on the luring of fish school were observed at a cage around a set net fishing ground using a manufactured underwater speaker. Underwater sounds that were emitted for the luring of fish school were the pure sounds of which frequency were 300Hz and 400Hz, engine noise and swimming sound. The results of the observation are as follows : 1. The input and output wave forms of a manufactured underwater speaker in water tank were similar to those in measurement frequencies. The result of the observation indicated that it could be used for the purpose of the sound emission in measurement frequencies. 2. The effect of the emitted pure sound of 300Hz, 400Hz was remarkable for the luring of fish school in 2 minutes after the sound emission. The reaction of fish school was more sensitive to the pure sound of 400Hz than 300Hz. 3. The effect of the emitted engine noise was more remarkable than that of the pure sound for 3 minute continuously. On the feeding sound, fish formed a shoal and swimmed, but didn't gather around the underwater speaker. 4. The feeding and swimming sound spectra on rudder Hsh showed similar sound pressure distribution each other, they appeared low sound pressure in frequencies of 200-600Hz.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.25 no.1
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• pp.12-17
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• 1989

A field experiment was carried out of confirm the effect of underwater sound on the luring of fish school of chub mackerel in the coast of Idousyo Island. Underwater sound that was made use of luring of fish school was pure sound and interval pure sound which the frequencies of the sound were 150Hz and 200Hz, respectively. The results of the observation of hooking and recording paper of fish finder indicate that the effect of emitting sound at 20m in the depth of water was remarkable for the luring of fish school of chub mackerel. The vertical pure sound pressure level at 150Hz and 200Hz of the water layer that was lured the fish school of chub mackerel were 140.1dB and 146.dB at 30m, 121.0dB and 126.6dB at 70m and 141.9dB and 120.5dB at 120m in the depth of water, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.324-328
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• 2019

There are several dedicated individual chambers for sports that are supplied and used, but none of them are multi-pressured all-in-one chambers that can provide a sport-multi environment simultaneously. In this study, we design a multi-pressure (positive / atmospheric / negative pressure) integrated chamber that can be used for the sport-multi-artificial environment system. We presented new chamber designs with enlarged space for the tall users and then carried out structural analysis with maximum stress and structural safety. Under the targeted allowable pressure conditions, maximum stresses occurred at the joint of the shell and the entrance, the structural safety of the chamber was evaluated with the allowable stress of its material. As a result of the structural analysis of the multi-pressure integrated chamber, the maximum stress for the positive pressure and negative pressure conditions was much smaller than the allowable stress of its material. And as a result of the structural safety evaluation, it was confirmed that the design of the final prototype for the chamber was structurally safe by satisfying the safety factor of 2 or more.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1991.04a
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• pp.175-181
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• 1991

정밀장비의 진동환경을 평가, 제어하기 위해서는 우선적으로 미진동 환경을 측정할 수 있는 장비와 기술이 필요하며, 방진 system 구성시 국내에서는 방진소재의 개발이 요구되고 있다. 그리고 진동에 민감한 정밀장비들을 사용 하는 반도체 및 정밀공장에서는 진동허용 기준을 나타내는 data sheet가 필 요하고 사용자측에서도 장비의 진동 test성적서를 장비구매시 제작사에 요구 할 필요성이 있다. TEM(투과형 전자현미경)의 경우 음압에 의한 가진문제도 대두되고 있으며 정밀장비가 최대의 성능을 발휘하기 위해서는 이러한 문제 를 검토해야 한다. 만일 국내에서 진동에 민감한 정밀장비를 제작시 장비의 진동 특성을 평가할 수 있는 실험장치와 기술이 필요하다.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.4 s.19
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• pp.36-43
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• 2004

In 1909 Hiram P. Maxim invented one of the first metal silencers for reducing sound levels in firearms. Silenced me have been mainly applied in the hunting and military operation. In particular special force make use of silenced rifle because it is low sound level. This paper considers experimental analysis for the characteristics of shock wave caused by shooting of a silenced me. Experimental results Indicate that the sound level of K-7 silenced rifle was lower than the sound level of MP5 silenced rifle. And, Sound Power Level of K-7 silenced rifle at a distance more than 75m or loom have nearly the constant value. This results that suggested the characteristics data about K-7 rifle's impulse noise will be apply to design the silencer of a small arms.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.06a
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• pp.8-11
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• 2013

스테레오-멀티채널 업믹스(Stereo-to-Multichannel Upmix)기술은 시장의 대부분을 차지하는 스테레오 음원을 홈시어터와 같은 멀티채널 스피커 재생 환경에서 효과적으로 재생하기 위한 채널 포맷 변환 기술을 말한다. 수평적인 공간감뿐만 아니라 수직적인 공간감을 재현하기 위하여 10.2, 22.2채널 환경의 경우 고도 채널이 추가되었다. 본 논문에서는 이러한 채널 환경에서 수직, 수평적인 공간감을 재현하기 위하여 새로운 초기 반사음을 생성하는 알고리즘을 제안하였다. 제안된 알고리즘은 진폭 패닝방법을 이용하여 전방의 가상 음원들에 의하여 발생되는 리시버 위치에서의 음압을 일치시킴으로써 기존 알고리즘이 가지지 못했던 이론적인 배경을 갖는다. 청취 평가 실험을 통하여 제안된 알고리즘은 음장의 수직, 수평적인 폭을 증가시키며, 좀 더 안정적인 음상 정위 성능을 가지는 것을 확인하였다.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2003.05a
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• pp.80-82
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• 2003

어군의 음향에 대한 행동을 알아내는 것은 어업에 있어서 중요한 일로, 많은 어종의 청각특성을 파악하는 것이 필요하며 많은 연구자들이 다양한 실험방법으로 측정하여 왔으며, 그 결과 어류도 어느 주파수대의 음을 감지하는 능력이 있다든가 음원 방향을 탐지하는 능력을 가진다는 것 등이 밝혀지고 있다. 이처럼 어류의 청각능력을 어업생산에 응용하기 위한 하나의 시도로서 음과 사료에 의한 학습, 즉 수중음향을 이용하여 어군의 유집행동을 유발하고, 어군을 학습시켜 어군의 행동영역, 섭이행동 등을 제어하기 위해서는 어느 주파수의 음을 어느 정도의 음압으로 방성할 때 어류가 들을 수 있는지, 어떤 음이 학습음으로 가장 효과적인지, 어느 정도의 기간동안 학습을 시켜야 학습효과가 명확하게 나타나고 가장 오랜 동안 학습효과를 유지시킬 수 있는지 등을 구명하는 일이 매우 중요하나 이에 관해서는 참돔, 넙치, 연어, 송어 등 극히 일부의 어종에 대해서만 연구되고 있는 실정이다. (중략)

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.4
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• pp.302-307
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• 2001

The underwater background noise measured in Geoje and Tongyoung diving fishing ground from May to December, 2000 and analyzed to get optimum carrier frequency and transmitter power level for underwater wireless telephone design. The results obtained are summarized as follows: 1. At the Geoje and Tongyoung diving fishing ground, the lowest ambient noise band was 25~30kHz with 57dB and 52dB re 1$\mu$Pa, respectively. 2. At the Geoje and Tongyoung diving fishing ground, the lowest noise band during fishing activity was 67dB and 62dB re 1$\mu$Pa, respectively. 3. At the Geoje diving fishing ground, the noise of water jetter which is a digging machine for subbottom shells was 102dB re 1$\mu$Pa. 4. Considering the design parameters of underwater wireless telephone, it is found that the optimum carrier frequency band is around 30kHz and the transmitter source level should be at least 131dB re 1$\mu$Pa for 500m range telephone.