Measurement of Underwater Acoustic Energy Radiated by Single Raindrops.

Shu Liu,Rui Tang,Qi Li,Dajing Shang,Qingming Zhang

doi:10.3390/s21082687

Abstract

Underwater noise produced by rainfall is an important component of underwater ambient noise. For example, the existence of rainfall noise causes strong disturbances to sonar performance. The underwater noise produced by a single raindrop is the basis of rainfall noise. Therefore, it is necessary to study the associated underwater noise when drops strike the water surface. Previous research focused primarily on the sound pressure and frequency spectrum of underwater noise from single raindrops, but the study on its sound energy is insufficient. The purpose of this paper is to propose a method for predicting the acoustic energy generated by raindrops of any diameter. Here, a formula was derived to calculate the underwater sound energy radiated by single raindrops based on a dipole radiation pattern. A series of experiments were conducted to measure the underwater sound energy in a 15 m × 9 m × 6 m reverberation tank filled with tap water. The analysis of the acoustic energy characteristics and conversion efficiency from kinetic to acoustic energy helped develop the model to predict the average underwater sound energy radiated by single raindrops. Using this model, the total underwater sound energy of all raindrops during a rainfall event can be predicted based on the drop size distribution.

Highlights

Rain and wind generated acoustic sound from the ocean surface represents the background baseline of ocean ambient noise
Once the average underwater acoustic energy for any type of single raindrop has been calculated, the total underwater sound energy for all raindrops during a rainfall event can be predicted based on the drop size distribution as generalized from the empirical
A series of experiments were conducted to measure the underwater acoustic noise produced by a raindrop when it falls onto a planar water surface at its terminal velocity

Summary

Introduction

Rain and wind generated acoustic sound from the ocean surface represents the background baseline of ocean ambient noise. There are two distinct acoustic fields associated with rainfall. The study of rainfall noise is important to marine physics to study wind and rainfall over the ocean [4] and for the use of sonars [5,6,7]. This is important for biologists when studying the impact of artificially generated sound on marine mammals [8]

Objectives

Results

Discussion

Conclusion