• Title/Summary/Keyword: Acoustic source

Search Result 935, Processing Time 0.038 seconds

Indentification of Noise Source of a Diesel Engine using Complex Acoustic Intensity Method (복소음향인텐시티법을 이용한 디젤엔진의 소음원 규명)

  • 오재응;김상헌;한광희
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.6 no.1
    • /
    • pp.182-195
    • /
    • 1998
  • The relation between the vibration induced from machinery and the radiated sound is complicated. Acoustic intensity method is widely used to obtain the accuracy of noise identification. In this study, as groundwork, the complex acoustic intensity method is performed to identify noise source and transmission path on different free space point source fields. From the numerical analysis for these simple fields, it is possible to predict the sound field characteristics which noise sources are related with each other, and certificate the validity of complex acoustic intensity. As an industrial application, the complex acoustic intensity method is applied a diesel engine to identify sound radiation characteristics in the near field.

  • PDF

Acoustic Analysis of Axial Fan using BEM based on Kirchhoff Surface (Kirchhoff Surface 변화에 따른 송풍기 소음의 BEM 해석)

  • 박용민;이승배
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2002.05a
    • /
    • pp.772-777
    • /
    • 2002
  • A BEM is highly efficient method in the sense of economic computation. However, boundary integration is not easy for the complex and moving surface e.g. in a rotating blade. Thus, Kirchhoff surface is designed in an effort to overcome the difficulty resulting from complex boundary conditions. A Kirchhoff surface is a fictitious surface which envelopes acoustic sources of main concern. Acoustic sources may be distributed on each Kirchhoff surface element depending on its acoustic characteristics. In this study, an axial fan is assumed to have loading noise as a dominant source. Dipole sources can be computed based on the FW-H equation. Acoustic field is then computed by changing Kirchhoff surfaces on which near-field is implemented, to analyze the effect of Kirchhoff surface on it.

  • PDF

Point-level deep learning approach for 3D acoustic source localization

  • Lee, Soo Young;Chang, Jiho;Lee, Seungchul
    • Smart Structures and Systems
    • /
    • v.29 no.6
    • /
    • pp.777-783
    • /
    • 2022
  • Even though several deep learning-based methods have been applied in the field of acoustic source localization, the previous works have only been conducted using the two-dimensional representation of the beamforming maps, particularly with the planar array system. While the acoustic sources are more required to be localized in a spherical microphone array system considering that we live and hear in the 3D world, the conventional 2D equirectangular map of the spherical beamforming map is highly vulnerable to the distortion that occurs when the 3D map is projected to the 2D space. In this study, a 3D deep learning approach is proposed to fulfill accurate source localization via distortion-free 3D representation. A target function is first proposed to obtain 3D source distribution maps that can represent multiple sources' positional and strength information. While the proposed target map expands the source localization task into a point-wise prediction task, a PointNet-based deep neural network is developed to precisely estimate the multiple sources' positions and strength information. While the proposed model's localization performance is evaluated, it is shown that the proposed method can achieve improved localization results from both quantitative and qualitative perspectives.

Estimation of Velocities of Acoustic Signals and Source Locations in PSC Beam by Acoustic Emission (AE기법을 이용한 PSC보의 음파속도와 음원위치 산정방법)

  • Youn, Seok-Goo;Lee, Changno;Kim, Eun-Kyum
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.26 no.5A
    • /
    • pp.917-925
    • /
    • 2006
  • Experimental tests were performed to estimate velocities of the acoustic signals through prestressed concrete beam and source locations using acoustic emission (AE) techniques. Seven AE sensors are mounted on the surface of 5m length test beam with equal spacing and using Schmidt Hammer AE events are made at 18 locations. The velocities of AE signals are estimated using the time differences of arrival times and the distances between the source locations and the AE sensor locations. In addition, using the Least Square Method, the AE source locations are re-evaluated reversely using both of the arrival times and the velocities of AE signals. Test results show the average velocity of the AE signals is about 4,000 m/sec and the velocity decreased with the increase of the distance from source locations to AE sensors due to the effect of attenuation. Based on the estimation of the source locations, it is observed that the errors of source locations are decreased when the velocities of each AE sensor are used rather than the average velocity.

Evaluation for Noise Reduction of the HVAC by Modification of CAM Curve (CAM 곡선 개선에 의한 차량용 공조기의 소음 저감 평가)

  • Jeong, J.E.;Jung, C.Y.;Seo, B.J.;Jeong, U.C.;Oh, J.E.
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.21 no.9
    • /
    • pp.787-797
    • /
    • 2011
  • The noise in a vehicle is an important factor for customers purchasing a car. Particularly, reduction of the noise that is generated from HVAC(heating, ventilation and air conditioning) is very important since it has considerable effects on interior noise. In general, identification of noise source is crucial to reduce noise level. The complex acoustic intensity method is widely used to obtain the accurate measurement and identification of noise source. Therefore, in the previous study, noise source of HVAC was identified through experimental approach using the complex acoustic intensity method. In this study, we are intended to confirm reduced level of noise by comparing the result between before and after modification of cam curve that is based on identified noise source of HVAC. It is found out that noise source of HVAC are motor and cam area using the complex acoustic intensity method in the previous study. We performed experiments to compare noise level between before and after modification of cam curve. Especially, it can be seen that complex acoustic intensity method using both active and reactive intensity is vital in devising a strategy for comparison to noise level. Also, the vector flow of acoustic intensity was investigated to identify sound intensity distributions and energy flow in the near field of HVAC.

Acoustic Source Power Control and Global Noise Reduction by Selection of Distribution and Impedance of Absorptive Materials in Acoustically Small Enclosures (흡음재의 배치와 임피던스 선정을 통한 음원 방사파워 제어와 전역 소음 감소)

  • 김양한;조성호
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.14 no.8
    • /
    • pp.668-674
    • /
    • 2004
  • The possibility of global noise reduction by the sound power control through selection of distribution and impedance of absorptive materials is discussed. It is necessary to investigate the relation between the global sound energy in the field and the total sound power radiated by sources. In the previous work,$^{(1.2)}$ the authors presented a useful design method to change boundary condition that can be useful to reduce noise in acoustically small enclosures. Changing boundary condition Is related to not only enclosure’s geometrical shape but also acoustical treatment on walls for example, attaching of impedance patches (ex: absorptive material). In many practical situations, we often meet situation to change acoustical treatment on walls. The possibility of total acoustic potential energy(globa1 noise) reduction by acoustic source power control is examined in an acoustically small cavity Using acoustic energy balance equation, the relation between global noise control performance and absorptive material’s arrangement/impedance is deduced. Numerical simulation is performed to interpret its physical meaning in terms of absorbent’s distribution and impedance.

Acoustic based Two Dimensional Underwater Localization Considering Directional Ambiguity (방향 모호성을 고려한 수중 음향 기반의 2차원 위치 추정 기술 개발)

  • Choi, Jinwoo;Lee, Yeongjun;Jung, Jongdae;Park, Jeonghong;Choi, Hyun-Taek
    • The Journal of Korea Robotics Society
    • /
    • v.12 no.4
    • /
    • pp.402-410
    • /
    • 2017
  • Acoustic based localization is essential to operate autonomous robotic systems in underwater environment where the use of sensorial data is limited. This paper proposes a localization method using artificial underwater acoustic sources. The proposed method acquires directional angles of acoustic sources using time difference of arrivals of two hydrophones. For this purpose, a probabilistic approach is used for accurate estimation of the time delay. Then, Gaussian sum filter based SLAM technique is used to localize both acoustic sources and underwater vehicle. It is performed by using bearing of acoustic sources as measurement and inertial sensors as prediction model. The proposed method can handle directional ambiguity of time difference based source localization by generating Gaussian models corresponding to possible locations of both front and back sides. Through these processes, the proposed method can provide reliable localization method for underwater vehicles without any prior information of source locations. The performance of the proposed method is verified by experimental results conducted in a real sea environment.

Hydroacoustic Records and Numerical Models of the Source Mechanisms from the First Historical Eruption of Anatahan Volcano, Mariana Islands

  • Park M.;Dziak R.P.;Matsumoto H.
    • 한국지구물리탐사학회:학술대회논문집
    • /
    • 2004.06a
    • /
    • pp.232-237
    • /
    • 2004
  • Anatahan Volcano in the Commonwealth of the Northern Mariana Islands (CNMI) erupted for the first time in recorded history on 10 May 2003. The underwater acoustic records of earthquakes, explosions, and tremor produced during the eruption were recorded on a sound-channel hydrophone deployed in February 2003. Acoustic propagation models show the seismic to acoustic conversion at Anatahan is particularly efficient, aided by the slope of the seamount toward the hydrophone. The hydrophone records confirm the onset of earthquake activity at 01:53Z on 10 May, as well as the onset (at ${\~}$06:20Z) of continuous, low-frequency (5-40 Hz) acoustic energy that is likely volcanic tremor related to magma intrusion. The hydrophone recorded a total of 458 earthquakes associated with the eruption. To predict the character of acoustic signals generated from Anatahan, we developed a moment-tensor representation of a volcano-seismic source that is governed by the geometry of the source and the physical properties of the magma. A buried magmatic pipe model was adopted, and numerically modeling source parameters such as the pipe radius and magma viscosity enable us to grasp the inward nature of Anatahan Volcano.

  • PDF

New Acoustic Imaging Method Development for Localization of an Underground Acoustic Source Using a Passive SONAR System

  • Jarng, Soon-Suck
    • The Journal of the Acoustical Society of Korea
    • /
    • v.18 no.2E
    • /
    • pp.10-17
    • /
    • 1999
  • The aim of the work described in this paper is to develop a complex underground acoustic system which detects and localizes the origin of an underground hammering sound using an array of hydrophones located about 100m underground. Three different methods for the sound localization will be presented, a time-delay method, a power-attenuation method and a hybrid method. In the time-delay method, the cross correlation of the signals received from the array of sensors is used to calculate the time delays between those signals. In the power-attenuation method, the powers of the received signals provide a measure of the distances of the source from the sensors. In the hybrid method, both informations of time-delays and power-ratios are coupled together to produce better performance of position estimation. A new acoustic imaging technique has been developed for improving the hybrid method. This new acoustic imaging method shows the multi-dimensional distribution of the normalized cost function, so as to indicate the trend of the minimizing direction toward the source location. For each method the sound localization is carried out in three dimensions underground. The distance between the true and estimated origins of the source is 28m for a search area of radius 250m.

  • PDF

A Study on the Effects of Parameter Sensitivity on Matched Field Processing

  • Park, Cheolsoo;Woojae Seong;Park, Hang-Soon;Lee, Kyu-Yeul
    • The Journal of the Acoustical Society of Korea
    • /
    • v.20 no.1E
    • /
    • pp.31-37
    • /
    • 2001
  • Matched Field Processing (MFP) is a successive process of correcting mismatches between true and assumed parameters by matching the measured acoustic field data with numerically simulated data which we call replica. The MFP is widely used both in geo-acoustic parameter inversions and in source localizations. Whether a certain parameter can be inverted effectively or whether a source can be localized correctly depends on the amount of the influence that a parameter has on the acoustic field during the matching process. Sensitive parameters can be better estimated than the less sensitive ones in MFP. On the contrary, the sensitive parameters affect adversely on the source localization results when they have uncertainties. In this paper, a sensitivity index is defined based upon the field variation resulting from the perturbed parameters. Numerical test results show that the index behaves in accordance with the results of source localization under a mismatched environment and also with the inversion solutions.

  • PDF