Quantitative evaluation for variability characteristics of reflected sound waves from sea surface

Many kinds of hydroacoustic devices are used in the field of ocean development of resources and observations. In evaluating the effect of sound propagation in water, it is important to evaluate the characteristics of sound reflection on sea surface. Amplitude and phase of reflected sound waves often fluctuates because of the changing sea surface with waves. In this paper, we evaluated the amplitude and phase variability characteristics of reflected sound waves on sea surface by acoustic simulation with the finite difference time domain method and water tank test. It is revealed that the energy ratio. for amplitude variability is uniquely determined by Rayleigh roughness parameter 2k sigma(z) when the sea surface is sufficiently random or the number of surface waves 2L/Lambda included in the irradiation range of sound waves is large. In addition, the standard deviation of phase sigma(theta) for the phase variability is determined by 2k sigma(z) regardless of Lambda, that is, sea surface spectrum. (C) 2019 The Japan Society of Applied Physics