LI Guangfang　  ZHAO Anbang　  HUI Junying　  WANG Yilin

(College of Underwater Acoustic Engineering, Harbin Engineering University  Harbin 150001)

Received Jun. 22, 2008

Revised Dec. 9, 2008

Abstract The splash sound of target's water entry is an instantaneous signal, consisting of impact component and bubble components. It is difficult to detect and estimate the azimuth of this signal by traditional azimuth estimation methods using a signal vector sensor, especially when the SNR is low. Empirical mode decomposition is a nonlinear analysis method that can emphasize signals' instantaneous characteristic. In this paper, the pressure and particle velocities are decomposed into different intrinsic mode functions (IMF), and the MAIA (mode acoustic intensity averager) method can realize the instantaneous signals' detection and azimuth estimation. The lake experiment and sea trial results show that this method can decompose water-entry sound and ambient interference into different IMFs, so as to detect the starting time of water-entry sound signal and estimate its azimuth effectively.　

PACS numbers: 43.30, 43.60