Sound Propagation Modeling

Ivansson, Sven

doi:10.1016/b978-0-12-811240-3.00003-5

Cited by 7 publications

(7 citation statements)

References 130 publications

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“…The gas domain (swimbladder geometry), water Figure 1 domain, and PML were meshed with a resolution of at least 10 mesh elements per wavelength at the highest frequency (200 kHz). The PML is the absorbing domain which acts as a non-reflecting boundary around the computational domain (water) to attenuate the waves limiting the boundary, where the incident pressure field and scattered field are computed 45 . The Kirchhoff -Helmholtz integral equation was solved in the frequency domain for each small element computing the far field backscattered pressure, as 45 :…”

Section: Backscatter Modellingmentioning

confidence: 99%

Characterization of European sprat acoustic backscatter

Palermino,

Gastauer,

Felice

et al. 2024

Preprint

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In fisheries acoustics, the identification of targets and precise translation of acoustic energy into biological meaningful metrics remains a challenge. Backscattering cross-section, or its logarithmic form, Target Strength (TS, dB re 1 m2), is a key parameter in this process. There are numerous studies on commercially important species, but few studies are available on commercially non-important species, such as the European sprat in the Mediterranean Sea. The application of backscattering models can improve our understanding of the acoustic properties of these species, allowing the manipulation of key parameters affecting the TS. Here we applied several backscattering models, on three-dimensional swimbladder shapes derived from Computer Tomography (CT) scans, of sprat collected during the MEDiterranean International Acoustic Survey (MEDIAS) in 2021. The theoretical TS pattern was compared with empirical TS revealing a good fit at 38 and 70 kHz between 0° (broadside incidence) and − 20° and significant differences at higher frequencies and tilt angles. This study provides estimates of the relative frequency response and broadband backscatter of sprat in the Mediterranean Sea. Moreover, the relationship of TS with fish length at 38 kHz yields a new relevant conversion parameter (b20) of -68.3 dB re 1 m2 for European sprat in the Mediterranean Sea.

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Section: Backscatter Modellingmentioning

confidence: 99%

Characterization of European sprat acoustic backscatter

Palermino,

Gastauer,

Felice

et al. 2024

Preprint

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“…Well established methods exist to compute the k m , n and the Z m , n ( z ) (e.g. [ 4 , 54 ]). For robust and automatic computations of the k m , n with winding-number integrals, it can be convenient to use quadruple precision.…”

Section: Coupled-mode Sh-wave Computationsmentioning

confidence: 99%

Coupled-mode separation of multiply scattered wavefield components in two-dimensional waveguides

Ivansson

2023

R. Soc. open sci.

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For a waveguide that is invariant in one of the horizontal directions, this paper presents a mathematically exact partial-wave decomposition of the wavefield for assessment of multiple scattering by horizontally displaced medium anomalies. The decomposition is based on discrete coupled-mode theory and combination of reflection/transmission matrices. In particular, there is no high-frequency ray approximation. Full details are presented for the scalar case with plane-wave incidence from below. An application of interest concerns ground motion induced by seismic waves, which may be severely amplified by local medium anomalies such as alluvial valleys. Global optimization techniques are used to design an artificial medium termination at depth for a normal-mode representation of the field. A derivation of a horizontal source array to produce an incident plane wave gives, as a by-product, an extension of a previous Fourier-transform relation involving Bessel functions. Like purely numerical methods, such as finite differences and finite elements, the method can handle all kinds of (two-dimensional) anomaly shapes.

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“…The source depth was set to 20 m, the frequency to 20 Hz, in accordance with big whale songs characteristics, and receiver depth to the considered OBS depth. As the height of the water column was over ten times the wave length ( 20 Hz = 75 m), the ray propagating model was considered to be realistic (Ivansson, 2017). The theoretical Time Difference of Arrivals (TDOA th ) of each S th were then calculated, considering only the first arriving ray provided by BELLHOP.…”

Section: Environmental Characteristicsmentioning

confidence: 99%

Baleen whale distribution and seasonal occurrence revealed by an ocean bottom seismometer network in the Western Indian Ocean

Dreo

Bouffaut

Leroy

et al. 2019

Deep Sea Research Part II: Topical Studies in Oceanography

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From the acoustic data acquired by the RHUM-RUM (Réunion Hotspot and Upper Mantle Réunions Unterer Mantel) Ocean Bottom Seismometer (OBS) network between October 2012 and November 2013, this study revealed baleen whale occurrence in the western Indian Ocean (IO). Low-frequency songs from three species (Antarctic Blue Whales, Pygmy Blue Whales and Fin Whales) as well as P-calls (or Spot-calls) from an unknown species were recorded on the dataset. The wide arrangement of the OBS network (2000 km × 2000 km) provided valuable information to draw seasonal patterns of occurrence and distribution all over the area. These species occurred sympatrically in the western IO, at least during austral autumn months emphasizing the importance of this region for these populations. This data set helped to refine the knowledge on their spatio-temporal distribution and complete the picture built by previous studies. A tighter sub-network of 8 OBSs deployed on the South West Indian Ridge provided ideal inter-sensor spacing for whale tracking. We demonstrated the capability of such array of detecting and tracking the three different whale species up to 50 km and for several hours. As a result and to understand the effect of acoustic wave propagation, songs from the tracking were described at a close and remote distance of the sensor. This work could also help to understand the local behavior of these species during austral autumn months in this area of the western Indian Ocean.

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Sound Propagation Modeling

Cited by 7 publications

References 130 publications

Characterization of European sprat acoustic backscatter

Characterization of European sprat acoustic backscatter

Coupled-mode separation of multiply scattered wavefield components in two-dimensional waveguides

Baleen whale distribution and seasonal occurrence revealed by an ocean bottom seismometer network in the Western Indian Ocean

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