Acoustics

Knowledge-building project for industry (KPN), funded by The Research Council of Norway and industry partners Equinor and Aker BP. The academic partners are NORCE (host institution), SINTEF, NTNU, Politecnico di Milano, and UiB.

The project objective is to develop knowledge for interpreting distributed acoustic sensing (DAS) data from production wells by maximum exploitation of new and previously acquired sensor data, combined with statistical processing methods, physical modelling, machine learning, and hybrid analytics. The project includes one post doc. position in the Acoustics group at UiB.

PhD project, CRIMAC Centre for Research-based Innovation.

PhD research fellow: Yngve Bøe, UiB. Supervisors: Audun O. Pedersen, UiB, Tonje Nesse Forland, Institute of Marine Research (IMR). Supervisory team members: Geir Pedersen, IMR, Babak Khodabandeloo, IMR, Per Lunde, UiB.

The objective of the PhD work is to acquire a better understanding of the acoustic signals scattered from single and multiple marine organisms and how they can be measured accurately and reliably with wideband echo sounders. This includes the frequency dependence of target strength of CRIMAC-relevant fish species.

The PhD fellow will collaborate closely within the CRIMAC consortium and with a parallel PhD project focusing on quantitative modelling of wideband echo sounder systems for measurement of target strength and volume backscattering coefficient.

PhD project, CRIMAC Centre for Research-based Innovation.

PhD research fellow: Helge Brøndbo Plassen, UiB. Supervisors: Audun O. Pedersen, UiB, Geir Pedersen, Institute of Marine Research (IMR). Supervisory team members: Tonje Nesse Forland, IMR, Babak Khodabandeloo, IMR, Per Lunde, UiB, Rolf J. Korneliussen, IMR.

The PhD candidate will work on methods to improve our understanding and use of modern wideband echosounder methodologies and acoustic signals scattered from marine organisms, employing mathematical and numerical modelling, supported by measurements in lab and field. The results shall provide an improved basis for further development of acoustic wideband methods in fisheries acoustics, with focus on abundance estimation, species identification, and size distribution.

The PhD candidate will collaborate closely within the CRIMAC consortium and a parallel PhD
project focusing on quantification of the wideband acoustic backscattering by single and multiple marine organisms.

PhD project, University of Bergen.

PhD research fellow: Wei Wang, UiB. Supervisors: Audun O. Pedersen, UiB, Per Lunde, UiB, Magne Vestrheim, UiB.

The work is aimed at investing and explaining the physical mechanisms underlying effects that have been observed in transmission of an ultrasonic beam through a solid plate immersed in a fluid. Such effects being observed both in experiments and by numerical simulations include

• signal enhancement ("signal amplification"),
• resonance frequency downshift,
• beam narrowing (energy concentration of the field transmitted through the plate)),
• distance-dependent additional minima and maxima in the transmitted field, and
• change of such characteristics with transducer ka number, transducer-plate distance, plate-hydrophone distance, plate material (Poisson’s ratio), angle of beam incidence, aperture of the receiving transducer, etc.

These effects are observed only for certain leaky Lamb modes, i.e., in certain frequency plate thickness regions: They appear to be observed only for leaky Lamb modes for which the corresponding Lamb mode posesses a backward wave branch, and only upon acoustic excitation in the frequency region of such a backward wave branch. For other modes and other frequency regions, such effects have not been observed. The results obtained so far indicate that these effects are caused by a combination of (i) dispersion of leaky Lamb modes in the plate, and (ii) diffraction of the incident sound beam to the plate. The effects appear to be closely related to the backward-wave frequency regions of the corresponding Lamb modes. Using experimental measurements in combination with quantitative numerical modelling, the PhD work will seek to investigate and determine

• which parameters of the sound field and the plate have influence on the above-mentioned effects,
• how these parameters influence the mentioned effects, and
• the connections between these effects, the backward wave branches of the corresponding Lamb modes, and the power flow field in the plate and the surrounding fluid.

That is, in essence, to investigate and determine influences of transducer aperture and transducer nearfield-farfield characteristics on the plate’s transmitted nearfield-farfield characteristics, over the frequency range of the lowest-order leaky Lamb modes in the plate, including backward wave branch(es) in the plate.

The understanding and utilization of these mechanisms may have significant influences on current and future industrial measurement methods.

PhD project, SFI Smart Ocean.

PhD research fellow: Julián Pelaez-Quiñones, UiB. Supervisors: Per Lunde, UiB, Peter Thomas, NORCE, Steinar Bjørnstad, Tampnet.

The project focuses on the use of fibre-optic cables to investigate natural and anthropogenic wavefields (primarily acoustic) in the ocean for diverse purposes, including ambient noise monitoring and source-medium characterization. This will mainly rely on the analysis of Distributed Acoustic Sensing (DAS) data, a trending photonics technology that maps strain and temperature changes along optical fibres at meter-resolutions over tens of kilometers.

PhD project, SFI Smart Ocean.

PhD research fellow: Amr Abboud, UiB. Supervisors: Per Lunde, UiB, Jan Kocbach, NORCE.

The subject of the project is non-destructive evaluation and structural health monitoring in wind turbine structures using ultrasonic guided waves.

PhD project as part of the FRIPRO project “Subsea gas energy and quality measurement using ultrasonic flow meters", funded by Research Council of Norway.

PhD research fellow: Eivind Nag Mosland, UiB. Main supervisor: Per Lunde, UiB.

See publication list on the personal page.

See personal page in Norwegian Research Information Repository.

See also the personal page.

M. M. Sæther (2024). Numerical Integration and Angular Spectrum Modeling of Resonant and Non-Resonant Wave Interaction with a Solid Plate. Journal of Theoretical and Computational Acoustics, 32(4), 2450006.

M. M. Sæther (2023). Customization of the angular spectrum method for calculating the acoustic piston field transmitted through a solid plate using MATLAB. MethodsX, 10, 102037.

M. M. Sæther, S. Almenningen, G. Ersland, and P. Lunde (2022). Compressional wave phase velocity measurements during hydrate growth in partially and fully water saturated sandstone. Fuel, 324, 124522.

M. M. Sæther, S. H. Midtbø, and P. Lunde (2022). Interaction of three-dimensional acoustic beam with fluid-loaded solid plate: Axial near-to far-field transmission at normal beam incidence. Ultrasonics, 125, 106795.

Mathias M. Sæther and Per Lunde, "Ultrasonic beam transmission in the backward and forward wave frequency wavenumber bands of a fluid embedded steel plate” in proceedings of the IEEE International Ultrasonics Symposium, Venice, Italy, 10-13 October 2022.

Mathias M. Sæther, Per Lunde, Magne Vestrheim, " Ultrasonic beam radiation from a piston source through a water-immersed steel plate using ASM. Pressure-to-pressure transfer function and numerical challenges," in Proceedings of the 44th Scandinavian Symposium on Physical Acoustics, online, 26 -29 January, 2021.

Mathias M. Sæther, Simen Midtbø, Per Lunde, Magne Vestrheim, "Nearfield effects from leaky Lamb modes in a steel plate for normal beam incidence," in Proceedings of the 43rd Scandinavian Symposium on Physical Acoustics, Geilo, Norway, 26 -29 January, 2020.

M. M. Sæther, P. Lunde, G. Ersland, " Elastic wave velocities under methane hydrate growth in Bentheim sandstones," in Proceedings of the 42nd Scandinavian Symposium on Physical Acoustics, Geilo, Norway, 27-30 January, 2019.

M. M. Sæther, "Elastic wave velocities and attenuation under methane hydrate growth in Bentheim sandstone. -Measurements and modelling." PhD thesis, University of Bergen, Bergen, Norway, 2018.

M. Sæther, P. Lunde, G. Ersland, "Sound velocity measurement methods for porous sandstone. Measurements, finite element modelling, and diffraction correction," in Proceedings of the 39th Scandinavian Symposium on Physical Acoustics, Geilo, Norway, 31 January-3 February 2016.

M. Sæther and P. Lunde, "Sound velocity measurement methods for porous sandstone. Discussion and preliminary results," in Proceedings of the 38th Scandinavian Symposium on Physical Acoustics, Geilo, Norway, 1-4 February 2015.

See personal page in Norwegian Research Information Repository.