• 제목/요약/키워드: Acoustic Transmission loss

검색결과 234건 처리시간 0.022초

음향강도계측법에 의한 음향투과손실의 측정 및 표면진동 모우드의 예측에 관한 연구 (A study of transmission loss and surface vibration mode by the two microphone acoustic intensity method)

  • 김의간;남청도;전효중
    • Journal of Advanced Marine Engineering and Technology
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    • 제11권1호
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    • pp.63-71
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    • 1987
  • The measuring of acoustic intensity has been investigated by many researchers and practicians during the last several decades. But due to the lack of measurement accuracy, they have had no practical use. In recent years, the two microphone acoustic intensity method has been developed by the advancement of FFT analysis technique and the digital data processing equipment. This new method of using two microphones gives informations on the noise source survey and the acoustic power of sound radiation source without the anechoic room. In this paper, theoretical formulae for the two microphone acoustic intensity method and the sound transmission loss are checked. The obtained results for the acoustical enclosure of gas heat pump were compared with the classical field incidence mass law. The surface vibration modes for a panel of enclosure were also estimated.

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하이브리드 방법을 이용한 배기계 소음 해석 (Noise Analysis of Intake System by Hybrid Method)

  • 이장명;한성수;임학종
    • 소음진동
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    • 제9권2호
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    • pp.310-316
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    • 1999
  • 4-Pole parameter method based on an acoustic theory is very popular for the analysis of the acoustic behavior of the car exhaust system. However, this method is applicable only for the simple shape of acoustic elements of the muffler. Numerical methods such as FEM(Finite Element Method) or BEM(Boundary Element Method) can also provide acceptable results for the acoustic analysis of the car exhaust system. Even though these numerical methods have benefits for the analysis of complicated shape of acoustic elements of the muffler, time consuming is another problem during modeling and numerical calculation. Combining benefits of both methods, the new code called the hybrid method for car exhaust system is introduced. And the developed code is utilized for calculation of the transmission loss of a main muffler of an automobile comparing with the experimental results.

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동심관형 공명기의 천공 분포 및 연장관이 전달 손실에 미치는 특성 해석 (Effect of Non-uniform Perforation and Extended Inlet/outlet Length in the Concentric Resonator on the Transmission Loss)

  • 이성현;이정권
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2005년도 추계 학술대회논문집(수송기계편)
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    • pp.114-117
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    • 2005
  • In the reactive concentric resonator, perforated inner tubes are widely used for various purposes related to noise reduction, flow guiding, and structural aspects. Perforation distribution patterns influence both the acoustic performance and mechanical performance. In this study, the influence of distribution patterns on acoustic performance are explained by adopting the concept of extended inlet/outlet length. Predicted transmission with varying extended inlet/outlet length is compared with prediction by varying distribution patterns. The transmission loss difference due to perforation distribution patterns can be explained by changing the extended inlet/outlet length of the uniformly perforated resonator.

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펄스 튜브를 이용한 수중 전달 손실 측정에서 간극이 미치는 영향에 대한 고찰 (A Study on the Effect of a Gap in Measurement of Underwater Transmission Loss by Pulse Tube)

  • 서윤호;김상렬;김재승;변양헌;서영수
    • 한국음향학회지
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    • 제34권3호
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    • pp.192-199
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    • 2015
  • 펄스 튜브를 이용하여 시편의 전달 손실 성능을 측정할 경우, 시편 설치를 위해 필연적으로 시편과 펄스 튜브 내벽 사이에 간극이 존재한다. 본 논문에서는 이와 같은 간극이 전달 손실 측정 결과에 미치는 영향에 대해 평가했다. 평면파에 대해 일정 폭 및 길이를 갖는 간극 전과 후 음압의 비를 구하여 전달 계수를 유도하고 측정 대상 시편의 전달 계수와 조합하여 간극이 포함된 시편의 전달 손실을 구했다. 이와 같은 해석 모델을 이론해가 존재하는 10 mm 두께의 스테인리스 스틸 시편에 적용하여 시험 결과와 비교함으로서 해석 모델의 적절성을 보였다. 마지막으로 해석 모델을 통하여 간극크기 및 시편 전달 손실 성능에 따라 전달 손실 측정에 미치는 영향을 분석했다.

누출이 헬름홀츠 공명기의 소음저감 특성에 미치는 영향 (Effect of Leakage on the Noise Reduction Characteristics of Helmholtz Resonator)

  • 이일재
    • 한국소음진동공학회논문집
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    • 제19권6호
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    • pp.634-640
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    • 2009
  • Helmholtz resonator has been used, especially in intake and exhaust systems of vehicles, due to its good noise reduction characteristics at low frequencies. Many approaches have been developed to predict the acoustic behavior of the resonator with the assumption that there is no leakage from the resonator. However, its behavior may be affected by leakage which may exist in manufacturing processes or on purpose. This study investigates the effect of leakage on the noise reduction characteristics of Helmholtz resonator with two practical examples. One is a resonator with a gap between baffle and housing of the resonator and the other one is a resonator with two drain holes on the baffle. The measured transmission loss shows that the resonance frequencies are considerably shifted to higher frequency due to the leakage. The Boundary Element Method was applied to predict the transmission loss of the Helmholtz resonator with drain holes. The comparison between the measured and predicted transmission loss shows that the acoustic impedance of the holes is essential for accurate predictions of the transmission loss.

자동차 흡기 소음 저감을 위한 다공질 관의 적용 (The Application of a Porous Duct for Reducing the Intake Noise of Vehicle)

  • 이장명;한성수
    • 소음진동
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    • 제11권1호
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    • pp.29-35
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    • 2001
  • Recently, the porous duct is becoming one of Possible ways to reduce the intake noise of an automobile instead of using resonators. In this article, acoustic characteristic of the porous duct is investigated theoretically and experimently. Futhermore, 4-pole parameter of the porous duct is introduced to predict transmission loss of it for various case. Acoustic efficiency of the porous duct is shown with experimental result using a car.

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수중 음향 환경에서의 영상 전송 성능 비교분석 (Performance Comparison of Image Transmission in Underwater Acoustic Environment)

  • 이승우
    • 한국군사과학기술학회지
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    • 제11권3호
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    • pp.19-29
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    • 2008
  • Underwater acoustic(UWA) communication is one of the most difficult field in terms of severe channel environments such as multipath propagation, high temporal and spatial variability of channel conditions. Therefore, it is important to model and analyze the characteristics of underwater acoustic channel such as multipath propagation, transmission loss, reverberation, and ambient noise. In this paper, UWA communication channel is modeled with a ray tracing method and applied to image transmission. Quadrature phase shift keying(QPSK) and multichannel decision feedback equalizer(DFE) are utilized as phase-coherent modulation method and equalization technique, respectively. The objective is to improve the performance of the image transmission using vertical sensor array instead of single sensor in the viewpoint of bit error rate(BER), constellation diagram, and received image quality.

초음파 센서를 이용한 수중통신기에 관한 연구 (A Study on the Underwater Communication system of Ultrasonic Transducer)

  • 김동현;오승재;황현석;송준태
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2000년도 춘계학술대회 논문집 전자세라믹스 센서 및 박막재료 반도체재료 일렉트렛트 및 응용기술
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    • pp.168-171
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    • 2000
  • Underwater acoustic communications have made considerable advances in the past decade. The purpose of this paper is to achieve the underwater communication by ultrasonic sensors and to investigate conditions of good underwater acoustic communicators. As a result of this experiments, the ultrasonic sensors, MA40E7R/S, made by Nicera can be used as ultrasonic transducers for underwater communication using AM(Amplitude Modulation) signal and Transmission Loss is 17.328[dB] at 65[cm]. To make a good underwater communicator, proper diameter of disk PZT transduers is the one of most important factors, because radiation of acoustic wave depends on proper diameter of transduers and the transmission loss strongly depends on the spreading loss.

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동해 아극전선 해역의 수중음향환경 및 저주파 음파전달 양상 (Underwater Acoustic Environment and Low Frequency Acoustic Transmission in the Sub-Polar Front Region of the East Sea)

  • 임세한;류건희
    • 한국군사과학기술학회지
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    • 제12권4호
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    • pp.415-423
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    • 2009
  • To investigate low frequency acoustic transmissions in the Sub-Polar Front(SPF) of the East Sea, numerical experiments are conducted with Range dependent Acoustic Model(RAM) using Circulation Research of the East Asian Marginal Seas(CREAMS) data and Autonomous Profiling Explorer(APEX)) data. Significant seasonal variations of sea water properties are existed across the Sub-Polar Front(SPF) region from the north and the south. The model results show that Transmission Loss(TL) decrease(about 20dB) with ideal front in the warm region whereas TL increase(about 25dB) with ideal front in the cold region. Regardless of season(both in summer and winter), when the sound source is located in the cold region of the SPF, the model results show weak TL, compared to the case of the source in the warm region(Maximum difference of TL reaches 28dB). This difference between the cases when the source is located in the cold region and the warm region, is accounted for from the different vertical profiles of sound speed in both regions.

펄스 튜브를 이용한 수중 음향 성능 측정 시스템 개발 (Development of Underwater Acoustic Performance Measurement System Using Pulse Tubes)

  • 서윤호;김상렬;이성민;변양헌;서영수
    • 한국소음진동공학회논문집
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    • 제24권5호
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    • pp.399-406
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    • 2014
  • Underwater acoustic materials are installed in order to reduce reflection, transmission and radiation of an underwater structure. The acoustic performance of the materials should be evaluated in accurately-controlled environment in terms of temperature and static pressure. In this paper, two pulse tubes, which are equipped with temperature and pressure controllers, are designed and developed to evaluate echo reduction(ER) and transmission loss(TL) of underwater acoustic materials. The procedures of the evaluation are suggested and the validation is carried out by comparing theoretical values to experimental results for a simple stainless steel specimen and free surface. In result, it is validated that developed pulse tubes are able to measure ER and TL with 2 dB tolerance.