The Effect of Attenuation from Fish on Passive Detection of Sound Sources in Ocean Waveguide Environments

Abstract

Attenuation from fish can reduce the intensity of acoustic signals and significantly decrease detection range for long-range passive sensing of manmade vehicles, geophysical phenomena, and vocalizing marine life. The effect of attenuation from herring shoals on the Passive Ocean Acoustic Waveguide Remote Sensing (POAWRS) of surface vessels is investigated here, where concurrent wide-area active Ocean Acoustic Waveguide Remote Sensing (OAWRS) is used to confirm that herring shoals occluding the propagation path are responsible for measured reductions in ship radiated sound and corresponding detection losses. Reductions in the intensity of ship-radiated sound are predicted using a formulation for acoustic attenuation through inhomogeneities in an ocean waveguide that has been previously shown to be consistent with experimental measurements of attenuation from fish in active OAWRS transmissions. The predictions of the waveguide attenuation formulation are in agreement with measured reductions from attenuation, where the position, size, and population density of the fish groups are characterized using OAWRS imagery as well as in situ echosounder measurements of the specific shoals occluding the propagation path. Experimental measurements of attenuation presented here confirm previous theoretical predictions that common heuristic formulations employing free space scattering assumptions can be in significant error. Waveguide scattering and propagation theory is found to be necessary for accurate predictions.

Optimal Automatic Wide-Area Discrimination of Fish Shoals from Seafloor Geology with Multi-Spectral Ocean Acoustic Waveguide Remote Sensing in the Gulf of Maine

“…The OAWRS technology has been shown to enable instantaneous population density quantification and continuous monitoring of fish populations over thousands of square kilometers, with space-time sampling rates tens of thousands to millions of times higher than line transect methods by employing the natural capacity of the oceans for long-range sound channeling at lower frequencies [3,4,6]. Fish populations and behavior have been studied with OAWRS over wide areas in the Mid-Atlantic Bite [3], the Gulf of Maine [7] and the Nordic Seas [8][9][10][11]. To summarize some key results, the instantaneous horizontal structures and volatile short-term behavior of very large fish shoals, containing tens to hundreds of millions of fish and stretching for many kilometers, have been revealed by OAWRS, including the presence of population density waves within the shoals that exceed fish swimming speeds [3,7].…”

“…Cod spawning shoals sizes quantified with OAWRS in Lofoten Norway, with spatial diameters of up to roughly 40 km, were used to help quantify conditions leading to Cod stock collapses [8]. These results have been obtained in tandem with advances in accurately predicting and modeling the acoustic scattering from marine life that makes OAWRS possible [6,7,[10][11][12][15][16][17][18][19][20] as well as with advances in equipment development for long-range, wide-area ocean acoustics sensing [21][22][23].…”

A Nonlinear Gradient-Coiling Metamaterial for Enhanced Acoustic Signal Sensing

“…Most recently, Xiang et al proposed a robust speech enhancement method based on U-Net and generative adversarial learning to achieve speech enhancement at extremely low SNR conditions using algorithmic post-processing [17]. However, in practical engineering applications, some useful information in acoustic signals is weak, such as harmonic signals caused by structural damage [18][19][20][21]. Conventional cost-effective electrical sensor devices may not be able to sense these weak useful feature signals, and samples doped with strong background noise are difficult to train reliable models using deep learning.…”

Underwater Sound Characteristics of a Ship with Controllable Pitch Propeller

“…These include ship health monitoring for prevention of shipboard machinery and structural failures, underwater environmental noise mitigation from man-made vehicles, as well as maritime surveillance and defence [1][2][3][4][5][6][7][8][9]. The sound radiated from an ocean vessel can limit detection ranges in both passive and active sonar systems for a wide range of ocean remote sensing applications [1,[9][10][11][12][13][14][15][16][17][18][19], as well as in ocean acoustic communication [20,21]. It may also impact the behavior and communication of marine organisms [22][23][24][25][26], such as fish [13,[27][28][29][30][31] and marine mammals [32,33].…”