The measurement of underwater sound with optical diffraction by liquid surface wave

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The measurement of underwater sound with optical diffraction by liquid surface wave Yang Miao1,2,a

, Yuncheng Jiang1, Zaihui Qiu1, Di Wu3

1 Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing, China 2 Beijing Key Laboratory of Advanced Manufacturing Technology, Beijing University of Technology, Beijing,

China

3 College of Engineering Science and Technology, Shanghai Ocean University, Shanghai, China

Received: 6 January 2020 / Accepted: 10 September 2020 © Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2020

Abstract The objective of this work is to detect underwater sound with light diffracted by liquid surface wave (LSW). An experimental setup for underwater detection with a converter is established. The diffraction patterns by LSW are obtained. By analyzing the fringes, the characteristics of those relating to both amplitude and wavelength of LSW and underwater sound are achieved. Meanwhile, the transformation model of waves from underwater into LSW is proposed. The dependence of the amplitudes on the diameter of the converter is obtained by utilizing droplet-floating model. Finally, a comparison between the model and the experiment supports these observations.

1 Introduction Optical measurement for liquid surface wave (LSW) has been on the frontline of both optical and surface wave researches in the past decades. Research in LSW and related technologies enriches the theory of LSW, vibrations and optical measurement and can be applied to a broad spectrum of potential applications and technologies. One of the phenomena in such area is that phase of laser can be modulated by LSW. This phenomenon is a tool which is defined as laser sonar employed to measure the properties of LSW. There is growing recognition that such laser-sonar technology may detect underwater sound [1–4]. Studies of diffraction pattern modulated by LSW continued to attract considerable research interest. We have established an experiment designed to examine the modulation by LSW. It was demonstrated that laser beam can be modulated by LSW into diffraction pattern. In addition, distribution of the pattern shows analytical relationship with LSW [5, 6]. According to previous studies, owing to modulation (acousto-optical diffraction between surface wave and laser beam), a novel method called laser sonar is proposed to detect underwater sound [7]. Their work focused on utilizing a columnar converter to achieve vibration transfer from underwater sound to LSW. The properties of underwater sound are visualized by their method. However, coupled mode between underwater sound and LSW is not fully understood. Such a technique cannot be used in detecting properties of underwater sound directly.

a e-mail: [email protected] (corresponding author)

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Eur. Phys. J. Plus

(2020) 135:755

The vibration caused by underwater sound transmits to liquid surface resulting in liquid surface movement vertically. A LSW can be generated when a vertically