Ocean Acoustics by Anatoly Kistovich & Konstantin Pokazeev & Tatiana Chaplina

Author:Anatoly Kistovich & Konstantin Pokazeev & Tatiana Chaplina
Language: eng
Format: epub
ISBN: 9783030358846
Publisher: Springer International Publishing

(6.1)

where , , .

The symbol means rounding to the nearest larger whole and to the nearest smaller whole.

The obtained ray representation of the field is valid when the reflection coefficients do not depend on the value of the angle of incidence of the ray on the interfaces. In the case of such a dependence, this fact should be taken into account in an explicit form, which naturally leads to certain changes in the formula (6.1), expressed in the fact that each reflection coefficient at each level of iteration of imaginary sources must be multiplied by a certain geometric coefficient.

In a real situation, the use of a ray representation (6.1) requires limiting the number of members used in it. The idea of such a restriction is that as the index increases in total, the distance from the imaginary source to the observation point increases , which leads to a decrease in the contribution from the source in the total field. From the obvious geometric consideration of the problem, it follows: The greater the value of the relationship , the greater the number of members to be taken into account in the representation (6.1).

If the source is not monochromatic but impulse, in (6.1) the view expressions should be replaced by the value , where is the source function.

An exhaustive description of the processes of sound wave propagation in layered structures is given in the book [1].

Spreading in the oceans and seas, sound waves are reflected from the bottom and at the water–air interface. Reflection of the sound from the water–atmosphere boundary is “soft”—the phase of the sound signal changes to the opposite, resulting in the total sound pressure at the water–air interface becoming zero. The water–air boundary in the majority of acoustic models is a completely reflective boundary. The surface of the sea, as a rule, is agitated, which leads to a diffuse reflection of sound waves (along with the mirror waves) and increases their attenuation. The presence of a large number of air bubbles in the near-surface layer of the ocean also increases the attenuation of sound.

The ocean floor and the seafloor reflect sound waves differently, and its reflective properties are characterized by a reflection coefficient—the ratio of the sound pressure in the reflected wave to the sound pressure in the incident wave.

The general ideas for the application of the ray approach to propagation problems in heterogeneous environments will be considered using the following physical situation as an example. Let the sound source be located in a plane-parallel homogeneous layer, on the boundaries of which the speeds of sound are equal, and at the source level the speed of sound is lower than at the boundaries. In terms of ray theory, all rays emanating from the source in the range (from the vertical) of angles will not be able to go beyond the layer boundaries, as they will be fully reflected internally. Here, is the speed of sound at the transmitter level, and the is the speed of sound at the boundaries.

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