Coherent and diffusive fields of underwater acoustic ambient noise

Abstract

In this paper, results of investigations of underwater ambient noise are presented based on statistical analysis of the acoustic pressure and three orthogonal components of particle velocity of a medium P(t), Vx(t), Vy(t), Vz(t). The mathematical analysis used includes cross-spectral characteristics, simple coherence functions, phase spectra, and an algorithm to split the noise field into anisotropic and isotropic fields. The above approach is applied to study the anisotropic and isotropic fields of ambient noise in the deep open ocean and in a coastal area. A fundamental feature of the anisotropic field that has been revealed is that the direction of the horizontal component of dynamic noise energy flux is similar to the surface roughness propagation direction.

A Possible Mechanism of Dynamic Ambient Ocean Noise Horizontal Energy Flow Forming

“…Our investigation s show that the noise energy ow vector in the frequency range of 282-800 Hz makes an angle between 0°and 30°with Z axis (according to the extent of surface roughness), that is, the acoustic noise energy in this frequency range is transported from the surface roughness to the bottom. In this frequency ranges the direction of the energy Ix, (t) horizontal component as is shown in [1,2] coincides with the surface wind roughness propagation direction (wind direction). In the frequency ranges of 447-562 Hz and 562-800 Hz the directions of energy transports in the horizontal plane differ not more than 10 as Fig.…”

“…As it was stressed previously [1][2][3], ambient dynamic energy ow (in the frequency range of 200-800 Hz) proceeds in two different directions : vertical one (from sea surface roughness to bottom) and horizontal one, coinciding with the direction of wind surface roughness propagation.…”

“…In this paper the authors examine the temporal dependencies of tp(t) and 3(t) for ambient noise energy ow in different frequency over the range of 1-800 Hz and discuss a possible way of forming of a horizontal dynamic noise energy ow, which we revealed and described previously [2]. The measuring facilities and technique are described in [2].…”

Sparse Bayesian Learning Based Direction-of-Arrival Estimation under Spatially Colored Noise Using Acoustic Hydrophone Arrays

“…However, the actual noise environment is often spatially anisotropic due to the effects of wind, waves, and noise from distant traveling vessels [7][8][9][10][11][12]. Shchurov et al [13] have studied the composition structure and coherence properties of the ambient noise field in detail through a large number of experimental observations. Their findings show that the ambient noise field can be divided into isotropic and anisotropic components.…”

“…They proposed the concept of vector phase technique, which extends the means of vector signal processing. In the field of vector hydrophone receiving environment noise, V. A. Shchurov [13] and M. Hawkes [14] have done extensive research. The theoretical expression for the correlation between the channels of a vector hydrophone in an isotropic noise field was derived.…”