For an acoustic receiver deployed at the bottom of the direct arrival zone of a submerged source at short horizontal ranges in deep ocean, the interference pattern of the direct and surface-reflected acoustic arrivals shows periodic modulation, which is directly related to the source depth, source frequency, and vertical arrival angle. In this work, the interference cycle presented in the frequency domain is used to extract the broadband source depth, with the vertical arrival angle obtained from the ratio of vertical acoustic intensity and horizontal acoustic intensity from the signal recorded by a single vector sensor. Experimental results demonstrate the source depth estimation without requiring knowledge of the ocean environment.

In the marine environment, the effects of the seafloor and subbottom elastic media on the propagation of very low frequency (VLF) sound wave should be considered. In order to understand the mechanism of seismoacoustic field propagation, a very-low-frequency sound propagation experiment was conducted in shallow water using seafloor-located acoustic vector sensor and ocean bottom seismometers (OBS) in December 2017. The water depth is about 100 m. Pulse sources detanoted at depths of 7 m and 50 m were employed to emit the VLF signals. Comparing the signals received by OBS with that of the acoustic vector sensor, a narrow-band wave package group at VLF had been observed, which was excited by the interaction of acoustic waves in water with the layered shear seabed. In this paper, the pulse signals are used to analyze the characteristics of sound propagation and spatial correlation, amplitude and phase structure of separated normal modes based on warping transform, horizontal and vertical acoustic energy flow at different ranges. The time arrival structure and time expansion of the elastic-bottom-induced wave package group and its relationship with source distance and depth are also analyzed.

No abstract