• Title/Summary/Keyword: 음향 파워 레벨

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Study of Optimum Operating Conditions of Thermal Acoustic Generator (열음향파 발생장치의 최적 작동 조건에 대한 실험적 연구)

  • Shin, Sang Woong;Oh, Seung Jin;Lee, Yoon Joon;Kim, Nam Jin;Chun, Wongee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.2
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    • pp.131-137
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    • 2013
  • This study deals with the effects of major geometric parameters on the sound wave output of a thermal acoustic system. The output power of the acoustic wave was dependent on the stack position, stack length, resonator tube length, and input power. In experiments, the maximum SPL was generated when the stack was placed between one-fourth to half, resonator and stack length were longer, and input power was increased. The frequency was recorded to be 437 and 885 Hz when the resonator tube length was 200 and 100 mm, respectively. Therefore, when the resonator tube length was shorter, a higher frequency was recorded.

Transmission Loss Prediction of KHST's Wall Section (KHST 차량 벽면의 투과손실값 예측)

  • Kim, Kwan-Ju;Yoon, Tae-Jung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11b
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    • pp.104-109
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    • 2002
  • The purpose of this study is to calculate transmission loss of KHST passenger vehicle's wall section accurately Typical transmission loss measurement of wall in the laboratory condition was carried out in advance, which is easier than KHST. Transmission loss results were compared with those by statistical acoustic method. Transmission loss values of KHST calculated by experimental method are compared with those from closed form solution.

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A Study on the Computation and Application of Sound Power Level for Road Traffic Noise of Renewal Area (개발 예정지역 도로교통소음 음향파워레벨 산정과 응용에 관한 연구)

  • Kim, Deuk-Sung;Chang, Seo Il
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.6 s.99
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    • pp.635-644
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    • 2005
  • This paper is. a study on relation between road traffic noise(RTN) and sound power level(PWL). At present, many experimental formulae and prediction formulae are used for prediction of RTN. But these formulae are difficult to appiy to the metropolitan area because these formulae are inaccurate in the different condition from reference condition. This paper calculate RTN and PWL of each prediction formula, choose the best one and make a noise map of the subject area. Procedure is as follows. First, calculate $L_{eq}$ of RTN using experimental formulae and prediction formulae. Second, calculate PWL using $L_{eq}$ of RTN and distance attenuation for point source at semi-free field. Third, choose the most accurate formula. And finally, make a noise map of the subject area at present and future. The result using noise map will be able to apply to application field. Noise mapping tool used on this paper is Raynoise program using Ray Tracing Method(RTM), Mirror Image Source Method(MISM) and Hybrid Method(HM).

Noise Map Analysis for the Design of Noise Barrier at School Site (학교부지의 방음벽 설계를 위한 소음지도 해석)

  • Yun, Junho;Kim, Wonjin
    • Journal of Korean Society of Environmental Engineers
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    • v.34 no.4
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    • pp.232-238
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    • 2012
  • In this study, the noise mapping simulation is executed to design an effective barrier reducing noise levels of a school site. The geographical features of the ambient site and the school buildings are modelled in detail in order to consider sound propagation, deflection, and absorption phenomena etc. The main sound source, sound power level of expressway, is estimated on the basis of measured noise levels at several points of the site. The noise mapping simulation is performed by using ENPro, environmental noise prediction program based on ISO 9613 to analysis the effectiveness of noise barrier. Consequently, the noise barrier is designed to meet an environmental noise standard and satisfy low cost and safety conditions.

Sound Power Level of Electric Home Appliances according to Measurement Method (측정방법별 가전제품의 음향파워레벨)

  • Kang, Dae-Joon;Gu, Jin-Hoi;Lee, Jae-Won
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.19 no.4
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    • pp.335-346
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    • 2009
  • 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. This results will help us predict the indoor noise level using the basic data of sound power level.

A study of polarized mode convertible, wavelength tunable optical filter utilizing acoustic barrier and acouxto-optic effect in $LiNbo_3$ ($LiNbo_3$의 음향광학효과와 음향파 장벽을 이용한 편광모드 변환형, 파장가변 광 필터에 관한 연구)

  • 임경훈;정홍식
    • Korean Journal of Optics and Photonics
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    • v.11 no.3
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    • pp.193-197
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    • 2000
  • A polarized mode convertible, wavelength tunable optical filters with acoustic barriers and acousto-optic effect have been produced in LiNb03 substrate utilizing the Ti double diffusion technique. Polarization conversion in excess of 81 % and a spectral width of -200 kHz (-1.83 nm) were achieved at a wavelength of 1551.6 nm and RF frequencies of 173.07 kHz and 173.05 kHz for both transverse electric (TE) and transverse magnetic (lM) input polarizations, respectively. The electrical driving power was 10.97 mW and reduced to about 10% of one for an optical filter without an acoustic barrier. A linear tuning rate of 8.2 nmlMHz and sidelobe intensity of -4 dB was demonstrated. rated.

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Prediction of Highway Traffic Noise - Estimation of Sound Power Level Emitted by Vehicles (고속도로 교통소음 예측-자동차 주행소음의 음향파워레벨 평가)

  • 조대승;오정한;김진형;김성훈;최태묵;장태순;강희만;이성환
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.12 no.8
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    • pp.581-588
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    • 2002
  • Precise highway traffic noise simulation and reduction require the accurate data for sound power levels omitted by vehicles, varied to road surface, traffic speed, vehicle types and makers, different from countries to countries. In this study, we have elaboratively measured Korea highway traffic noise and parameters affecting noise levels at the nearside carriageway edge. From numerical simulation using the measured results for highway traffic noise, we propose not only two correction factors to enhance the accuracy of Korea highway traffic sound power estimation using ASJ Model-1998 but also its typical power spectrum according to road surface type. The measured and predicted highway traffic noise levels using the proposed sound power show little difference within 1 dB.

Acoustic Field Analysis of Reverberant Water Tank using Acoustic Radiosity Method and Experimental Verification (음향라디오시티법을 이용한 잔향수조 음장 해석과 실험검증)

  • Kim, Kookhyun
    • Journal of the Society of Naval Architects of Korea
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    • v.56 no.5
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    • pp.464-471
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    • 2019
  • The acoustic power is a major acoustical characteristic of an underwater vehicle and could be measured in a reverberant water tank. In order to obtain accurate measurement results, the acoustic field formed by the sound source should be investigated quantitatively in the reverberant water tank. In this research, the acoustic field of a reverberant water tank containing an underwater sound source has been analyzed by using an acoustic radiosity method one of the numerical analysis methods suitable for the acoustic analysis of the highly diffused space. The source level of the underwater sound source and acoustical properties of the water tank input to the numerical analysis have been estimated by applying the reverberant tank plot method through a preliminary experiment result. The comparison of the numerical analysis result with that of the experiment has verified the accuracy of the acoustic radiosity method.