• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.32 no.10
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• pp.17-21
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• 2003

국내 화장실 양변기의 배수 및 세정소음에 관한 실험실 측정결과를 소개하고자 한다. 1989년 대한주택공사에서 조사한 설문조사에 의하면 공동주택에서 외부로부터 들리는 소음에 대한 불만을 조사한 결과, 바닥충격음, 급배수설비 소음, 그리고, 공기전달음의 순으로 나타났다. 이와 같이 급배수시 발생소음은 공동주택 입주자의 주요한 민원중의 하나이다. 급배수설비 소음은 유체의 유동에 의하여 발생하며, 직접 공기중을 전파하여 가는 “공기전달음”과 배관지지 재료 및 구조체 등을 통해 재차 공기중을 전파하여가는 “고체전달음” 으로 구분된다. 여기서 “공기전달음”이란 실내에서 발생한 소리가 구조체를 진동하고 구조체는 인접실의 구조체 주변의 공기를 진동하여 소리가 방사되거나 또는 인접실간에 열려 있는 통로를 거쳐 전달되는 소음을 말하고 “고체전달음”이란 음원이 접하고 있는 건물구조체를 통하여 진동의 형태로 전달되는 소음을 일컫는다. 공동주택에서 배수관은 아래층 천장배관에 해당되므로 배수관에서 발생하는 소음은 아래층으로 직접 전달된다. 이러한 배수설비 소음은 배관재의 종류, 배관스페이스의 구조 및 위치 등에 따라 소음레벨이 달라지게 된다.(중략)

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.380-383
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• 2006

최근 소득수준이 높아짐에 따라 쾌적한 주거환경에 대한 욕구가 높아짐에 따라 소음에 대한 민원이 증가하고 있는 추세이나, 아직까지 변압기 소음에 대한 체계적인 대책을 세운 사례는 전무한 실정이다. 본 논문에서는 변전소의 주 소음원인 변압기의 소음을 예측하기 위하여 소음레벨을 수치적으로 해석하는 변압기 소음예측 프로그램을 개발하였다. 또한 소음민원이 예상되는 한 변전소를 선정하여 소음예측 시뮬레이션과 실제 소음측정을 통하여 그 결과를 비교하였다.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.4
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• pp.492-502
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• 1995

This paper describes the relationship between the behavior of the snakehead ( Channa arps) of 44cm long and the environmental noise levels due to the piling work. The experiment is conducted in the aquafarm located near Asan lake, Pyongtaek in 1993. The fish trajectory is obtained by a biotelemetry system in which a pulsed ultrasonic pinger attached onto the dorsal is tracked three dimensionally, and the noise and the vibration levels both in air and in water are measured. The results of this study are as follows: 1) The noise levels in water and in air and the vibration level measured at a distance of 90m from the noise source, increased by 36.5dB $(re\;l{\mu}Pa)$, 2308$(re\;0.0002{\mu}bar)$ and $5.9{\mu}m$ repectively compared to the levers before piling. 2) The highest variation of the swimming speed was observed right after the piling works and the width of variation decreased with the elapsed time. The average speeds of the fish before and during the works were measured as 0.8 times and 1.1 times of the body length, respectively. 3) It is found that the fish escapes into the mud of the aquafarm when a heavy shock wave occurred. Consequently, the heavy shock by the piling works could produce a considerably unfavorable effect to the fish.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.34-40
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• 2006

The daytime(7 a.m to 10 p.m.) and the nighttime(10 p.m. to 7 a.m.) used to calculate existing $L_{dn}$ is different from the domestic daytime(6 a.m to 10 p.m.) and nighttime(10 p.m. to 6 a.m.) periods. The difference of a time periods makes too difficult for converting measured $L_{eq}$ during daytime($L_d$) and nighttime($L_n$) periods to $L_{dn}$. Thus, it is difficult to directly compare with $L_{dn}$ standard of a foreign country. The pupose of paper is to propose a proper experimental equations that make up for the problems. The data of this paper used road traffic noise data of Auto-Network System(ANS) that generates $L_{eq}$ TNI, $L_{NP}$ for 1 hour. A method of this paper is as follows.(1) The data of ANS converted 24 hour $L_{eq}$ which measured every 1 hour to existing $L_{dn}$ and to $L_{dn}$ of an experimental equations.(2) The existing Lan is compared to results of $L_{dn}$ from experimental equations. The paper proposes a three experimental equations. This paper select an approximate equation that was most similar, to existing $L_{dn}$ out of these equations. When $L_{eq}$ data of different daytime and nighttime periods are converted to $L_{dn}$, an experimental equation of this paper can be used and applied to $L_{dn}$'s calculation.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.4
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• pp.348-355
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• 2000

This paper described the relationship between the behavior of the Israeli carp, Cyprinus carpio and the environmental noise level due to the dynamite explosion work. The experiment was conducted in the cage ($L10{\times}W4{\times}D4 m$) of aquaculture located at Chungjoo Lake, Chechon, in 1997. The fish trajectory was obtained by the telemetry system in which a pulsed ultrasonic pinger ($50 kHz, {\phi}16{\times}L70 mm$) attached to the fish was tracked three dimensionally, and the underwater noise levels were measured. The results of the study were as follows: 1. The underwater noise levels in the normal blasting measured at a distance of 400 m from the source of noise increased by $40 dB (re 1 {\mu}Pa)$ compared to the levels before explosion. The dominant frequency and the increased power spectrum level of the underwater noise by the explosion work were $75 to 100 Hz and 22.9 to 35.3 dB$, respectively. 2. The underwater noise levels in the test blasting measured at a distance of 350 m from the source of noise increased by average $49.5 dB (re 1 {\mu}Pa)$compared to the levels before explosion. 3. The swimming area of the fish was reduced with the time after explosion, and after more than one hour the fish represented the similar swimming area and behavior to the status of right before explosion. 4, The swimming depth layer of the fish was most of the case at the sea surface less than 1,0 m except during explosion or right after of it. But the fish swam downward when an external stimulus like the explosion noise was given to the fish. 5. The average swimming speeds of the fish before, during and after the works were about 1.2 times, 1.9 times and 1.0 times of the body length, respectively, and the speed of the fish with explosion was faster 1.6 times than the speed without of that. Consequently, the explosion noise levels measured by this study were sufficiently high to affect the fish, and the heavy shock by the explosion works could produce a considerable unfavorable effects to the fish.

• Tunnel and Underground Space
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• v.11 no.1
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• pp.14-19
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• 2001

The estimation of proper prediction method and the transformation method of environmental regulation standard were carried out by measuring blasting vibration. Vibration velocity was more adequate than vibration level in the blasting design by scaled distance. Thus, design and construction mutt be controlled by vibration velocity, and it is required that the vibration velocity is transformed to vibration level to meet regulation standard. Three transformation methods were studied. First, transformation formula is derived from the shock vibration data only. The second method it the transformation by correlation equation of vibration velocity and vibration level measured at the same time. The last one is the transformation of vibration velocity by FFT. It seems to be difficult to estimate damages by these methods because that every method shows considerable error. But transformation formula of PPV component to vibration level was most practical.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.920-923
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• 2004

천공 요소는 자동차나 공조기 등의 유체기계의 흡/배기계에 널리 사용된다. 천공요소는 일반적으로 유동과 소음원이 동시에 존재하는 환경에서 사용되며, 유동 및 음압 레벨의 변화에 의해서 큰 영향을 받게 된다. 천공요소의 임피던스의 변화는 소음기의 음향학적 특성에 영향을 미치게 되므로, 유동이나 음압 조건이 임피던스에 미치는 영향에 대한 연구가 중요하다. 본 연구에서는 통과하는 유동이 존재하는 천공요소의 임피던스를 실험을 통하여 측정하고 경계요소법을 사용하여 예측하였다. 측정 및 예측된 임피던스를 무차원화 해석을 수행하여 영향을 미치는 인자들을 분석하였다.

• Journal of dental hygiene science
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• v.15 no.5
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• pp.603-611
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• 2015

This research is aimed at cutting off hearing loss and other harmful factors due to noise and providing basic material for noise reduction plan. As the research method, this research assessed noise by measuring acoustic pressure level and frequency in various situation of non-treatment and treatment. As the measurement result, average noise degree of high speed handpiece of non-treatment, ultrasonic waves scaler, and low speed handpiece showed 58~66 dB(A). Average noise degree of scaling of treatment, tooth elimination, and denture adjust showed 73~81 dB(A). The result is inferior to recognized standards of noise induced hearing loss. But the result of assessing this with (noise rating) NR curve was NR-73~78, which exceeded general workplace noise standard. This level can cause hearing loss when exposed to a long time. Therefore, treatment office noise during dental treatment can cause psychological and physical damage in dental clinic employees, and it is urgently required to establish systematic and active noise reduction plan.

• The Journal of the Acoustical Society of Korea
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• v.41 no.4
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• pp.389-396
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• 2022

This paper aims to identify the causes and mechanisms of contraction-expansion noise in refrigerators and proposes noise reduction methods. Contraction-expansion noise generated in refrigerators is mainly due to stick-slip phenomenon occurring on the contact surface between inner parts. Friction experiments were conducted to identify the factors causing the stick-slip phenomenon. Furthermore, the vibration level of the internal components was measured to determine the characteristics and location of the contraction-expansion noise. Based on the experimental results, experiments have been conducted to verify the noise characteristics for each factor. From this, it was confirmed that the friction experiment and the refrigerator contraction-expansion noise generation location and frequency were the same. The vibration level also increased as the vertical force was increased due to load loading. Also, it was confirmed that the contraction-expansion noise was reduced when the surface roughness was increased. Therefore, it was concluded that increasing the surface roughness of the contact surface in the same way as the results of the friction experiment was the method of reducing contraction-expansion noise.

• The Journal of the Acoustical Society of Korea
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• v.29 no.3
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• pp.184-190
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• 2010

Lowering of auditory caused by noise is increased, these days. Especially, people who have noise induced hearing loss by permanent exposure to noise are increased according to spread out of multimedia and improvement of information equipment. The pure tone audiometry used in the hospital presently inspect auditory manually up to 8,000 Hz bandwidth. So the case of noise induced hearing loss which suffered from extended high frequency over 8,000 Hz, there is a problem to prevent hearing loss by precognition. In this paper, we proposed a method to prevent noise induced hearing loss by using extended high frequency bandwidth from 12,000 Hz to 20,000 Hz. We have got a experimental result to fifty of twenties who are often used to earphones through portable equipment. As a result, 36% of twenties show lowering of auditory caused by noise and 2% of them shows severe loss of hearing.