• 한국음향학회지
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• 제14권5호
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• pp.11-19
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• 1995

본 논문에서는 불규칙한 노면이 설치된 섀시 동력계(chassis dynamometer)로 부터 가진된 타이어의 구조 진동 소음을 음장의 공간적 변환기법을 이용하여 측정하였다. 음장의 공간적 변환기법은 소음원으로 부터 원거리까지의 전파를 계산하는 기법이다. 즉, 한평면의 음향 측정으로 부터 측정 평면에서 멀리 떨어지거나 더 가까운 평면에서의 음장을 표현하는 변수들인 음압, 음향 인텐시티, 입자속도 등을 계산한다. 측정 평면에서 음원쪽으로 가까운 평면의 계산은 관접음장 홀로그래피를 적용하여 계산하고 먼 쪽은 헬름흘쓰 적분식을 적용한다 측정결과로 부터 타이어 구조 진동 소음의 방사형태와 소음원의 위치를 예측하였다.

• 한국음향학회지
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• 제21권8호
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• pp.703-707
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• 2002

새로운 콘트롤 밸브 소음 예측 방법을 제안하고 밸브 및 배관으로 이루어진 시스템에 적용하여 그 가능성을 할인하였다. 기존의 소음 예측 방법은 무향실을 이용하는 기존의 예측방법보다 일반 산업체에서 시험 시설을 설치하기가 용이한 장점이 있다. 측정된 음향파워를 이용하여 소음예측식을 결정하고 상대유량계수 0.11인 경우 소음예측식에 따라 유량 및 차압의 변화에 따른 음향파워레벨을 평가하였고 그 결과가 측정값과 잘 일치함을 확인하였다. 제안된 밸브소음 예측기법은 콘트롤밸브의 소음특성을 나타내는 지표로서 사용할 수 있다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.332-339
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• 2007

As the economy has grown and the main industry in Korea has been changed from secondary industry to tertiary industry, the importance of indoor environment has been a matter of common concern, in which one of the main concerns is to improve the indoor acoustic conditions. However, even though this is required more than before, there are no measures to protect the human being from the noise of electric home appliances. This is owing to the absence of the data about sound power level of electric home appliances. So, we investigate the sound power level of them and analyze the acoustical characteristics of each one. First, we tried to investigate the sound power measurement method of each electric home appliance. After it we test the sound power level of them. From the survey, we can know that the vacuum cleaner is the most noisy electric home appliance, and the refrigerator is the least noisy one. The noise of a range hood is distributed over a wide range frequency. Lastly, we intented to propose the proper method measuring sound power level on each electric home appliance.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1540-1548
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• 2000

Sound intensity techniques and ODS(Operational Deflection Shape) techniques are applied to identify the acoustic noise source of a hard disk drive and its control system. The sound intensity is used to visualize the noise source locations, and the ODS information to visualize the vibration pattern and to obtain the dynamic characteristics of the noise sources. The measurement systems are customized to accurately measure the sound intensity and ODS distributions of HDD system in space domains as well as frequency domains. The measurement systems for the sound absorption and transmission loss of materials are also used to support the background data for the efficient noise control. Using the visual information of source locations and its dynamic characteristics, the partial noise barrier structure and optimum absorption are designed and its controlled sound power level is proved to be under 3.1 Bel(Idle)/3.3Bel (Seek) which is the lowest level in the disk drive industry.

• 한국소음진동공학회논문집
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• 제14권11호
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• pp.1123-1128
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• 2004

An experimental study on firing noise of K2 rifle was performed. Firing noises of K2 rifle were measured at close distance to rifle. Firing noise of K2 rifle which made in Korea, has not measured before. The measurement of firing noise at close distance is not simple, because the amplitude of firing noise is much bigger than the measuring limit of ordinary sound level meter even though it uses a signal attenuator. The measurement of firing noise at close distance is necessary for noise source positioning and for obtaining the sound power of K2 rifle. By this experimental study, the firing noise levels of K2 rifle at different positions are obtained and these data can be used to Predict the sound pressure level at any distance from muzzle of the rifle. Also these data can be used to calculate the threshold shift of gunner's ear.

• 한국해양공학회지
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• 제13권2호통권32호
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• pp.99-107
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• 1999

Boiler high-temperature pipelines such as main steam pipe, header and steam drum in fossil power plants are degraded by creep damage due to severe operationg conditions which are high temperature and high pressure for an extended period time. Such material degradation leads to various component failures causing serious accidents at the plants. Conventional measurement techniques such as replica method, electric resistance method, and hardness test method have such disadvantages as complex preparation and measurement procedures, too many control parameters, and therefore, low practicality and they were applied only to component surfaces with good accessibility. In this paper, artificial creep degradation test and ultrasonic measurement for their creep degraded specimens have been carried out for the purpose of evaluation for creep damage which can occur in high-temperature pipeline of fossil power plant. Absolute measuring method of quantitative ultrasonic measurement for material degradation was established, and long term creep degradationtests using life prediction formula were carried out. As a result of ultrasonic tests for crept specimens, we confirmed that the sound velocity decreased and the attenuation coefficient linearly increased in proportion to the increase of creep fractiin(${\phi}$c).

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.979-982
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• 2007

The effect of a scattering wall surfaces on sound diffusion can be assessed by determining the scattering and diffusion coefficients in the laboratory. However, the sound field in a concert hall including scattered reflections is different from the laboratory measurement condition. Therefore, there is a need for objective investigation of diffusion in real sound fields. In this paper, possible acoustical parameters of in-situ measurements are discussed.

• 비파괴검사학회지
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• 제20권1호
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• pp.18-26
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• 2000

화력발전소 보일러 고온배관인 주증기관, 헤드 및 증기드럼 등의 설비들은 장시간동안 고온고압의 가혹한 조건으로 운전됨에 따라 크리프손상에 의해 열화되고 있다. 이들 설비의 크리프손상측정에 적용되는 종래의 비파괴기법인 레프리카법, 전기저항법 및 경도법 등은 복잡한 측정절차 및 접근성, 검사결과의 신뢰도 및 측정정도 등 여러가지면에서 단점이 많다. 따라서 본 논문에서는 화력발전소 주요 고온배관에서 발생되는 경년열화인 크리프손상에 대한초음파 측정연구를 수행한 결과로서, 고온배관재료인 Cr-Mo강의 크리프 인공열화재를 대상으로 이들에 대한 크리프손상 상태별 초음과 음속(sound velocity) 및 감쇠(attenuation)의 초음파 신호특성을 평가하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계 학술대회논문집(수송기계편)
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• pp.122-125
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• 2005

This study is an measurement and prediction of transmission loss through dash panel with multi-path in a vehicle. Measurement results of transmission loss are derided by sound power measured using the sound intensity method under locating a sound source in the anechoic room and reverberant room, respectively. Prediction one is decided by multi-path analysis of dash panel composed by a various part of materials and complicated shape. Finally, two results show a great agreement between measured and predicted transmission loss.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.818-821
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• 2005

The sound measurement procedures of IEC 61400-11 are applied to field test and evaluation of noise emission from 1.5 MW wind turbine generator (WTG) at Yongdang and 660 kW WTG at Hangwon in Jeju Island. Apparent sound power level, wind speed dependence and third-octave band levels are evaluated for both of WTGs. 1.5 MW WTG at Yongdang is found to emit lower sound power than 660 kW one at Hangwon, which seems to be due to lower rotating speed of the rotor of WTG at Yongdang. Equivalent continuous sound pressure levels (ECSPL) of 660 kW WTG at Hangwon vary more widely with wind speed than those of 1.5 MW WTG at Yongdang. The reason for this is believed to be the fixed blade rotating speed of WTG at Yongdang. One-third octave band analysis of the measured data show that the band components around 400-500 Hz are dominant for 1.5 MW WTG at Yongdang and those around 1K Hz are dominant for 660 kW WTG at Hangwon.