• Title/Summary/Keyword: underwater sound

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Energy Spectrum of Underwater Explosive Sound (수중 폭발음의 에너지 스펙트럼)

  • Kim, Sung-Boo
    • The Journal of the Acoustical Society of Korea
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    • v.9 no.3
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    • pp.56-61
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    • 1990
  • A New theoretical energy spectrum model for underwater explosive sound is introduced in order to calculate the precise spectral energy levels. This model is obtained by Fourier analysis of Gaussian formula which accurately represents the pressure wave generated from Underwater explosions. In case that explosive energy is very low. The spectrum levels which are obtained from the new theoretical model are in good agreement with the experimental spectrum levels, while the Weston model using impulse formula cannot interpret the experimental results.

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Analysis of Low-frequency Reverberation Inshallow Water (천해에서의 저주파 잔향음 분석)

  • 박길선;나정열;최지웅;오선택;박정수
    • The Journal of the Acoustical Society of Korea
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    • v.20 no.4
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    • pp.94-100
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    • 2001
  • In October 1997, low-frequency reverberation was measured at an experimental site off the west coast of the Jeju island using the explosive charge, Signals Underwater Sound (SUS). Received signals were separated into the noise, the reflection, and the scattering region, and then were analyzed for the spectral and statistical characteristics of each region. In the analysis of the spectrum we verified that each region had a unique frequency band and statistical characteristics as well. The results of this analysis showed that the real and imaginary portions were shown to be both normal distributions in each frequency bin. The reverberation envelope had a Rayleigh distribution and the phase had a uniform distribution.

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Ranging Algorithm of Underwater Acoustic Wave with Look-up Table (Look-up table을 이용한 수중 음향파 거리 추정 알고리즘)

  • Cheon, Ju-Hyun;Moon, Seung-Hyun;Lee, Ho-Kyoung
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.4
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    • pp.23-29
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    • 2015
  • In this paper, we introduce a underwater ranging algorithm with Look-up Table (LUT) by modifying the existing method which is using the changes of angles of accoustic rays with SSP (Sound Speed Profile). We compare the horizontal distance errors and the calculation times. Our new algorithm exploits Time of Arriva l(ToA) - horizontal distance table based on SSP. This algorithm offers faster calculation speed than the previous one with the slight increase of the distance estimation error.

Study on the Underwater Acoustic Properties of Polyurethane Elastomer

  • Shin, Hyun Dai;Ahn, Byung Hyun
    • Elastomers and Composites
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    • v.52 no.4
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    • pp.326-331
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    • 2017
  • Two kinds of polyurethane elastomers were prepared and their acoustical properties underwater investigated. Their dynamic mechanical properties were measured using a dynamic mechanical analyzer. The sound speed and echo reduction in the 1-50 kHz frequency range were calculated from the data obtained using the analyzer. The sound speed, transmission and attenuation cofficient in 300-800 kHz were measured in a water-filled tank. Impedance tube experiments were performed to determine the reflective coefficient and echo reduction in the 3-8 kHz range. The polyurethane elastomer containing a hollow glass sphere showed a lower reflective coefficient and a higher echo reduction than the polyurethane elastomer without a filler.

Navigation System of UUV Using Multi-Sensor Fusion-Based EKF (융합된 다중 센서와 EKF 기반의 무인잠수정의 항법시스템 설계)

  • Park, Young-Sik;Choi, Won-Seok;Han, Seong-Ik;Lee, Jang-Myung
    • Journal of Institute of Control, Robotics and Systems
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    • v.22 no.7
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    • pp.562-569
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    • 2016
  • This paper proposes a navigation system with a robust localization method for an underwater unmanned vehicle. For robust localization with IMU (Inertial Measurement Unit), a DVL (Doppler Velocity Log), and depth sensors, the EKF (Extended Kalman Filter) has been utilized to fuse multiple nonlinear data. Note that the GPS (Global Positioning System), which can obtain the absolute coordinates of the vehicle, cannot be used in the water. Additionally, the DVL has been used for measuring the relative velocity of the underwater vehicle. The DVL sensor measures the velocity of an object by using Doppler effects, which cause sound frequency changes from the relative velocity between a sound source and an observer. When the vehicle is moving, the motion trajectory to a target position can be recorded by the sensors attached to the vehicle. The performance of the proposed navigation system has been verified through real experiments in which an underwater unmanned vehicle reached a target position by using an IMU as a primary sensor and a DVL as the secondary sensor.

A study on the weldability of TMCP steel plates in underwater wet arc welding (TMCP강의 습식수중 아크 용접성에 관한 고찰)

  • 오세규;김민남
    • Journal of Welding and Joining
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    • v.5 no.4
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    • pp.28-35
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    • 1987
  • The feasibility of underwater wet arc welding process is experimentally investigated by using high titanium oxide type electrodes and TMCP steel plates as base metal. It is assertained the tis process may be put to practical use. Main results are summarized as follows; (1) Sound underwater weld can be obtained by skilled welding operator, if proper welding conditions are selected. (2) In underwater wet arc welding process, the mechanical properties of HAZ are depend upon welding condition and the optimum welding condition can obtained. (3) The maximum hardness in the HAZ of TMCP steel plates is increased significantly in this welding process.

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Design of an Acoustic band Interpolator for Underwater Sensor Nodes (수중 센서 노드를 위한 음파 대역 인터폴레이터 설계)

  • Kim, Sunhee
    • Journal of Korea Society of Digital Industry and Information Management
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    • v.16 no.1
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    • pp.93-98
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    • 2020
  • Research on underwater sensor networks is increasing due to such reasons as marine resource management, maritime disaster prediction and military protection. Many underwater sensor networks performs wireless communication using an acoustic sound wave band signal having a relatively low frequency. So the digital part of their modem can take charge of carrier band signal processing. To enable this, the sampling rate of the baseband band signal should be increased to a sampling rate at which carrier band signal processing is possible. In this paper, we designed a sampling rate increasing circuit based on a CIC interpolator for underwater sensor nodes. The CIC interpolator has a simple circuit structure. However, since the CIC interpolator has a large attenuation of the pass band and a wide transition band, an inverse sinc LPF is added to compensate for frequency response of the CIC interpolator. The proposed interpolator was verified in time domain and frequency domain using ModelSim and Matlab.

A Method for the Selection of Underwater Multimedia Routing Protocol Stack based on the Similarity Model (유사성 모델 기반의 수중 다중매체 통신 라우팅 프로토콜스택 선택방법)

  • Shin, DongHyun;Kim, Changhwa
    • Journal of Korea Multimedia Society
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    • v.25 no.1
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    • pp.61-71
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    • 2022
  • When communication such as light, radio wave, or magnetic field is used underwater, the communication distance is very short, so sound waves are mainly used. However, by combining the strengths of each medium and communicating, stable communication may be possible. Underwater multi-media communication requires a protocol stack that supports it, which is very complex. To this end, this paper proposes a standard protocol stack and modeling technique to enable easy protocol stack modeling for the purpose. In fact, in this paper, a random model was created and analyzed through the proposal of modeling elements and similarity measurement methods, and as a result, it was analyzed that it was very helpful in creating a new model based on a standard model.

Determination of a New Cut-off Frequency Coefficient for Sound Propagation in the Surface Duct (표층도파관 내에서의 새로운 Cut-off 주파수 계수결정)

  • 김성부
    • The Journal of the Acoustical Society of Korea
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    • v.1 no.1
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    • pp.37-44
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    • 1982
  • In the mixed layer when the frequency approaches the cut-off frequency for the first mode of notmalmode theory, sound ceases to be trapped. Based on the data of surface sound velocities abtained during the period of 16 years in the Sea of Japan. A new cut-off frequency coefficient in the surface duct that will determine the miximum wave length for duct transimission of underwater sound has been calculated.

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Analysis of passive time-reversal communication performance in shallow water with underwater sound channel (음향채널이 존재하는 천해에서의 수동 시역전 통신 성능 분석)

  • Choi, Kang-Hoon;Kim, Sunhyo;Choi, Jee Woong;Kim, Hyeonsu;Kim, Byoung-Nam
    • The Journal of the Acoustical Society of Korea
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    • v.37 no.1
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    • pp.21-30
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    • 2018
  • A passive time-reversal technique can improve error performance of the underwater communication system by reducing influence of inter-symbol interferences, which is caused by a multipath channel response. The passive time-reversal communication system equipped with numerous receivers generally can obtain superior error performance since larger diversity gain can be obtained as the number of available received signal increased. In this paper, we analyze the optimal number and combination of receivers that can approximately achieve the best error performance when using the limited number of receivers. For this analysis, we use communication data collected during SAVEX15 (Shallow-water Acoustic Variability Experiment 2015) carried out in the south-western part of Jeju Island from May 14 to May 28, 2015. Analysis results show that there are depths of energy concentration due to the channel characteristics in which the underwater sound channel are present, and the passive time-reversal technique using the limited number of the receivers can derive near-optimal communication performance if the receivers for time-reversal processing are located at the depths where energy is concentrated.