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1

Vortex features of acoustic intensity vector in the shallow water

Shchurov V., Kuleshov V., Cherkasov A.

Hydroacoustics

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2011

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Vol. 14

209-216

EN

The vortex structure of acoustic intensity vector in the shallow water depending on a distance and frequency emitting was researched basing on the natural in-situ experiment. The experiment was fulfilled using the combined acoustic receivers in the Peter the Great Bay in the Japanese Sea. When axes x and y of rectangular system of coordinates being located in horizontal plane of the combined receiver, axis z was directed from surface to bottom. The receiver was submerged to ~70 m depth at the site depth of ~120 m; sound velocity on the surface was higher than that of the bottom’s one. To determine the vorticity there were calculated three components of rotor of intensity vector then, their histograms of distribution of probability density were plotted. In the work there were presented distribution histograms of the vorticity probability density of intensity vector for 110 Hz frequency under the different distances between source and receiver within ~1000–5000 m. In the case of single source the highest density of probability corresponds to magnitude of š1 for x- and y- norm components of rotor and 0 – magnitude for its z-component. As follows from the experiment the steady vorticity of acoustic intensity vector was observed along the entire distance (~4000 m) from source to receiver. The described mechanism of acoustic intensity transfer opens new possibilities in the research of acoustic features in the shallow water. The fixed vortex structures pose an interest as for physical acoustics, as for applied challenges of undersea acoustics.

2

On cross-processing scalar and vector quantities in underwater acoustics

Shchurov V., Kuyanova M., Tkachenko H., Kuleshov V.

Hydroacoustics

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2006

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Vol. 9

159-170

3

The observation of reverberation in the ocean by acoustic combined receiver

Shchurov V., Dorozhko B., Kuyanova M.

Hydroacoustics

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2005

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Vol. 8

185-192

EN

Results of observation of low-frequency tone pulse reverberation in deep open ocean by means of the combined sensor are presented. As the experiment showed, net energy flux density vector of the echo-signal carries information on properties of scattering directionality. The paper shows that the energy flux density vector of the field of surface –scattered low-frequency sound has both random and regular contributions. The regular contribution can be identified as the diffraction spectrum of scattered sound that is in line with the theory developed by L. Brekhovskikh. Lifetime of regular orderly structures existing in surface roughness is no less than 96 s as the experiment proves. The surface roughness diffraction lattice is likely to be built of swell waves.

4

Expectative noise-immunity of combined receiver

Shchurov V.

Hydroacoustics

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1999

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Vol. 2

229--234

EN

Simplified estimation of signal-to-noise ratio of combined receiver involving pressure receiver (scalar receiver) and particle velocity receiver (vector receiver) was performed. Combined receiver gain in SNR was introduced in much the same way as antenna array gain. It was shown that this quantity may be used to estimate expectative noise-immunity of combined receiver in actual noise fields.