Title page for etd-0723109-133711


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URN etd-0723109-133711
Author Ni-hung Cheng
Author's Email Address No Public.
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Department IAMPUT
Year 2008
Semester 2
Degree Master
Type of Document
Language zh-TW.Big5 Chinese
Title Application of Adaptive Algorithm on Analysis of
Spatial Energy of Ocean Ambient Noise
Date of Defense 2009-07-03
Page Count 96
Keyword
  • Adaptive Algorithm
  • Ambient Noise
  • Directionality
  • Beamforming
  • Spatial Coherence
  • Beam Resolution
  • Abstract Ocean ambient noise is one of factors that can affect the performance of sonar and underwater communication system, it can degrade the performance of sonar system on listening or active detection, and also can affect the quality of underwater communication. Due to the variation of temperature and density in the ocean which make ambient noise has directionality. Beamforming can analyze the directionality of noise energy. Conventional beamforming is based on the assumption of plane wave sound field, so the energy from each angle is obtained by linear accumulation of every element. However plane wave assumption may not be satisfied because of the boundary interactions of sound propagation and energy attenuation of water column, therefore conventional beamforming may have poor beam resolution and SNR in applications. This research is to study of the influence of spatial coherence of ambient noise on beam resolution, and to improve the beam resolution by using the adaptive algorithm from the communication system theory. Firstly, simulations were performed to study spatial coherence between plane wave and non-plane wave in ambient noise, and the results were compared with beam resolution. This research also analyzes the influence of different conditions of noise spatial coherence on beamforming with ASIAEX data. The results showed that ambient noise has lower spatial coherence at high frequency, and the beamforming has poor beam resolution because of the lower spatial coherence in noise. Therefore, the adaptive beamforming were performed to improve the beam resolution, and compared with the conventional beamforming. The results showed that the highest improvement on beam resolution is 42.9 %, and increased SNR by 6 dB. On the other hand, the application of ASIAEX data show that, the highest improvement on beam resolution is 40.0 %, and increased SNR by 8 dB. The noise notch of ambient noise became more significant by increasing in beam resolution, and it also promoted the accuracy of analysis on noise directionality.
    Advisory Committee
  • Shiuh-Kuang Yang - chair
  • Mei-Chun Yuan - co-chair
  • Ruey-Chang Wei - advisor
  • Files
  • etd-0723109-133711.pdf
  • indicate in-campus access immediately and off_campus access in a year
    Date of Submission 2009-07-23

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