Title: Method for the distinguish of normal modes in shallow water under near field

Author(s): ZHU Hanhao; XIAO Rui; ZHU Jun; ZHENG Guangxue; TANG Jun; TANG Yunfeng;

Affiliation(s): Institute of Marine Science and Technology, Zhejiang Ocean University; State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences; Institute of Naval Architecture and Mechanical-electrical Engineering, Zhejiang Ocean University; Key Laboratory of Ocean Observation-Imaging Testbed of Zhejiang Province, Zhejiang University; College of Underwater Acoustic Engineering, Harbin Engineering University

Abstract: This paper proposes a method to distinguish the normal modes in shallow water under near field. The method, which is based on frequency-wavenumber (F-K) transform, employs the 2D matrix comprising near field horizontal multi-channel signals. These signals are transformed from the time-space domain to the frequency-wavenumber domain, and the normal modes in the signals are distinguished by extracting the wavenumbers component at each frequency for each order in the frequency-wavenumber domain. The practical reliability and validity of this method are verified by performing numerical simulation and a tank experiment, and the results showed that the normal modes in the Pekeris waveguide below 200 Hz could be obtained reliably at 500 m by using this method.