Instrumentation and Methods for Acoustical Monitoring of the Sea of Japan Shelf
Victor A. Akulichev, Sergey I. Kamenev, Yury N. Morgunov, Anatoly V. Nuzhdenko, Sergey I. Penkin
Pacific Oceanological Institute Far Eastern Branch, Russian Academy of Sciences 43, Baltiyskaya Str., Vladivostok 690041, Russia
Abstract
Experimental results on determination of impulse characteristic of the acoustic waveguide are obtained. There are technical characteristics of the transmitting and receiving systems described. They have been tested, and at present the systems are used o carry out field experiments on the Sea of Japan shelf.. The theoretical calculations are compared with the observational data.
1. Introduction
The application of acoustic tomography methods by using complex signals includes analysis of information about conditions of sound propagation on the travel, along with such important things as development of transmitting and receiving acoustic systems, algorithms of signal processing and solution of inverse problems. Of special interest are the kinematic characteristics of acoustic fields on the stationary travels, for instance, phase and group velocities, considering that many tomographic problems are formulated in the terms of those ones [1]. Group delay time, gliding angle, vertical and horizontal wave numbers can be referred to the kinematic characteristics which are calculated by phase and group velocities. Ascertained in the works [2,3] for different types of waveguides is the relationship between phase and group velocities, with the concept of an invariant of spatially frequency interference structure of acoustic field being used. The impulse characteristic therewith can be considered as a distribution of the group delay time of acoustic field components (modes or arrays).
If the stationary white noise η(t) with the correlation function (N/2)δ(τ), where δ(τ) -delta-function, arrives at the input of linear system which the acoustic waveguide relates to, the impulse characteristic p(t) of the linear system, within a constant factor (N/2), matches with the cross-correlation function Rζη(τ) between input stationary white noise, exciting the system, and output random processζ(t)[4]. Based upon this determination, one can estimate the distortions
