Modelling acoustic propagation in realistic ocean through a time-domain environment-resolving ocean model.

The new generation of non-hydrostatic and compressible numerical models of the ocean can explicitly simulate acoustic waves when and where space and time resolution is adapted. We show that these models can consequently propagate accurately acoustic waves and modes through a free-surface, stratified ocean evolving simultaneously both in space and time, bringing them to the state of the art of acoustic propagation modelling. To some extent, both numerical cost and memory footprint may temper their range of applications but they are an unprecedented tool to evaluate deterministically the effects of ocean variability on low-frequency acoustic propagation in a realistically-evolving ocean.

A numerical approach to model sound generation by ocean dynamical processes: The case of surface gravity waves.

The new generation of regional ocean models can provide the evolution of both the slow and fast components of pressure, consequently opening original opportunities to evaluate the acoustic signal generated by ocean slower dynamical processes. This capacity is evaluated in the case of surface waves, with a focus on the hydro-acoustic precursors and on the acoustic modes induced by supersonic surface wave groups. The consistency with theory confirms that such models are adapted to answer recent interrogations by Wunsch [(2022).

Canonical correlation analysis as a statistical method to relate underwater acoustic propagation and ocean fluctuations.

Numerical models are currently used to understand how environmental fluctuations impact acoustic propagation. Such a process can be tedious in complex fluctuating environments. This letter proposes a complementary approach based upon canonical correlation analysis (CCA) to determine statistical relationships between two sets of observed acoustic and oceanographic variables.

Roughness influence on multibeam-subbottom-profiler specular echoes and roughness parameter inversion.

Integral solutions for wave scattering over slightly rough surfaces generally include the source and receiver directivity. In this paper, it is shown that integrating the point source, point receiver solution over the source and receiver apertures leads to solutions with a clear physical interpretation. The scintillation, time-of-arrival, and direction-of-arrival spatial covariances of the specular echo are derived for a multibeam-subbottom-profiler configuration and result in surface integrals that can be evaluated numerically.

Ambient noise dynamics in a heavy shipping area.

The management of underwater noise within the European Union's waters is a significant component (Descriptor 11) of the Marine Strategy Framework Directive (MSFD). The indicator related to continuous noise, is the noise levels in two one-third octave bands centered at 63Hz and 125Hz. This paper presents an analysis of underwater noise in the Celtic Sea, a heavy shipping area which also hosts the seasonal Ushant thermal front.

On the consideration of motion effects in the computation of impulse response for underwater acoustics inversion.

The estimation of the impulse response (IR) of a propagation channel may be of great interest for a large number of underwater applications: underwater communications, sonar detection and localization, marine mammal monitoring, etc. It quantifies the distortions of the transmitted signal in the underwater channel and enables geoacoustic inversion. The propagating signal is usually subject to additional and undesirable distortions due to the motion of the transmitter-channel-receiver configuration.