Browsing by Author "Tollefsen, Dag"
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Forsvaret i verdensrommet
Hofoss, Espen; Aarønæs, Lars; Abrahamsen, Trond; Tollefsen, Dag (2023-06)Rommet gir Forsvaret store teknologiske og strategiske muligheter – først og fremst innenfor kommunikasjon, navigasjon og overvåking. I dette magasinet kan du lese mer om disse mulighetene, og hva som må til for at vi ... -
Multiple-array passive acoustic source localization in shallow water
Tollefsen, Dag; Getstoft, Peter; Hodgkiss, William S. (2017)This paper considers concurrent matched-field processing of data from multiple, spatially-separated acoustic arrays with application to towed-source data received on two bottom-moored horizontal line arrays from the SWellEx-96 ... -
Probabilistic estimation of merchant ship source levels in an uncertain shallow-water environment
Tollefsen, Dag; Hodgkiss, William S.; Dosso, Stan E.; Bonnel, Julien; Knobles, David P. (2021-11-13)The estimation of ship source levels (SSLs) in shallow-water environments can be complicated by sound interaction with the seabed. Uncertainty in seabed properties influences SSL estimates, and it is of interest to mitigate ... -
Seabed characterization with a small towed array - simulation of system design facors
Tollefsen, Dag (2013-07-01)This report studies design factors for a small activated towed-array system for use in seabed characterization. By seabed characterization is here meant the estimation of geo-acoustic parameters including sound speed, ... -
Seismic exploration noise reduction in the marginal ice zone
Tollefsen, Dag; Sagen, Hanne (2014)A sonobuoy field was deployed in the Marginal Ice Zone of the Fram Strait in June 2011 to study the spatial variability of ambient noise. High noise levels observed at 10–200 Hz are attributed to distant (1400 km range) ... -
Ship source level estimation and uncertainty quantification in shallow water via Bayesian marginalization
Tollefsen, Dag; Dosso, Stan E. (2020-04-17)This paper applies a non-linear Bayesian marginalization approach to ship spectral source level estimation in shallow water with unknown seabed properties and uncertain source depth. The algorithm integrates the posterior ... -
Ship-of-opportunity noise inversions for geoacoustic profiles of a layered mud-sand seabed
Tollefsen, Dag; Dosso, Stan E.; Knobles, David P. (2019-04-30)This paper considers the use of broadband noise from a ship-of-opportunity in statistical inference for estimating geoacoustic parameters of a layered mud-sand seabed model via trans-dimensional (trans-D) Bayesian matched-field ... -
Source Localization With Multiple Hydrophone Arrays via Matched-Field Processing
Tollefsen, Dag; Dosso, Stan E. (2016)This paper considers approaches to combining information from multiple arrays in matched-field processing (MFP) for underwater acoustic source localization. The standard approach is to apply conventional MFP for each array ... -
Summary report on analysis of acoustic data from the SWASI-99 array experiment
Eidem, Ellen Johanne; Jenserud, Trond; Søstrand, Knut A.; Tollefsen, Dag (2003)The localization of underwater acoustic sources in a shallow water environment is addressed. Two array signal processing methods suitable for low-frequency signals in shallow water have been applied to data from an ... -
Three-dimensional multiple-source focalization in an uncertain ocean environment
Tollefsen, Dag; Dosso, Stan E. (2013)This letter develops a Bayesian focalization approach for three-dimensional localization of an unknown number of sources in shallow water with uncertain environmental properties. The algorithm minimizes the Bayesian ... -
Under-ice mid-frequency acoustic transmissionand communication in two Arctic Oceanenvironments
Tollefsen, Dag; Walree, Paul van; Jenserud, Trond; Forsmo, Vidar (2023-02-23)This paper presents data from mid-frequency (4−8 kHz) under-ice acoustic transmission and communication experiments in the Nansen Basin and in the Beaufort Sea of the Arctic Ocean. Measured impulse responses to range ~10 ... -
Wind- and tidal driven ambient noise in seasonallyice-covered waters north of the Svalbard archipelago
Tollefsen, Dag; Buen, Helge (2022-08-24)This paper presents analysis of a 1-year (2018–2019) recording of ambient noise (40–2000 Hz) at a seasonally ice-covered location on the continental slope between the Svalbard archipelago and the Nansen Basin, northeast ...