Searched for: +
(1 - 20 of 129)

Pages

document
Ainslie, M.A. (author), Weston, D.E. (author), TNO Fysisch en Elektronisch Laboratorium (author)
article 1996
document
Mountain, J.A.R. (author), Ainslie, M.A. (author), Martin, P.L.R. (author), Hughes, M.R. (author), Seto, L.Y. (author), Laker, R.A. (author), Robins, A.J. (author), TNO Fysisch en Elektronisch Laboratorium (author)
The merits of monostatic and bistatic geometries in terms of the evasion probability for area and barrier searches were described. Detection probabilities were calculated by generating signal excess surfaces for a given sonar geometry. Acoustic modeling and operational analysis allowed to detect the impact of the problem on performance and...
article 2001
document
TNO Fysisch en Elektronisch Laboratorium (author), Muller, S.H.E. (author), Ainslie, M.A. (author), Boek, W. (author), Simons, D.G. (author)
Active sonar reverberation returns offer the possibility to invert for geo-acoustic bottom parameters to characterise the underwater environment. We present the results of synthetic inversions of reverberation returs generated with a ray-based reverberation model in which bottom scattering is modelled according to a modified Lambert's rule. The...
conference paper 2002
document
Ainslie, M.A. (author), Robins, A.J. (author), TNO Fysisch en Elektronisch Laboratorium (author)
article 2003
document
Ainslie, M.A. (author), TNO Fysisch en Elektronisch Laboratorium (author)
The reflection of a plane acoustic wave from the seabed is considered. Conditions for the generation of an interface wave in a thin unconsolidated sediment layer overlying a solid substrate are examined, with particular attention to a resonance excited at lowfrequency and near grazing incidence. Assuming that the sediment layer can be treated as...
article 2003
document
Ainslie, M.A. (author), TNO Fysisch en Elektronisch Laboratorium (author)
A rigorous application of the traditional definition of sonar equation terms leads to the appearance of an unexpected factor, not routinely included, equal to the ratio of the characteristic impedance at the receiver to that at the source. An omission of this factor can lead to non-negligible errors for realistic conditions. It is further argued...
article 2004
document
Ainslie, M.A. (author), Robins, A.J. (author), Simons, D.G. (author), TNO Fysisch en Elektronisch Laboratorium (author)
A compilation of analytical formulas is presented, describing ray properties of a family of sediment sound speed profiles. The profiles are described as "generalized power law" profiles because they are generalizations of a similar family of simpler power law profiles considered in earlier work [M. A. Ainslie, J. Acoust. Soc. Am. 96, 2506–2515 ...
article 2004
document
TNO Fysisch en Elektronisch Laboratorium (author), Ainslie, M.A. (author)
Long range acoustic propagation in isothermal conditions is considered, involving multiple reflections from the sea surface. If the sea is calm there is almost perfect reflection and hence low loss. The effect of wind is to increase propagation loss due to the interaction with near-surface bubble clouds and rough surface scattering. Both...
conference paper 2004
document
Ainslie, M.A. (author), Morfey, C.L. (author), TNO Defensie en Veiligheid (author)
article 2005
document
Blarzino, G. (author), Ainslie, M.A. (author), Boek, W. (author), Simons, D.G. (author), Snellen, M. (author), TNO Defensie en Veiligheid (author)
The design of a bistatic short-range, shallow water reverberation model is presented, which aims to reproduce the reverberation measurements carried out by TNO, TUS, FFI and KDA in the Vestfjorden area (Norway), during the RUMBLE project. These were collected by using a Low Frequency Active Sonar (LFAS) source received on a towed horizontal...
conference paper 2005
document
Jenserud, T. (author), Plaisant, A. (author), Ainslie, M.A. (author), TNO Defensie en Veiligheid (author)
This paper presents results obtained during the EUCLID project RTP 10.16 called “RUMBLE” carried out with contribution of several European organisations: TUS in France, TNO-FEL in the Netherlands, KDA, FFI and NGU in Norway. The objective was to assess the capability of an Active Low Frequency Sonar to estimate bottom parameters in shallow water...
conference paper 2005
document
Ainslie, M.A. (author), TNO Defensie en Veiligheid (author)
The frequency dependence of the normal incidence amplitude reflection coefficient R of the seabed is considered for a range of frequencies ranging from 2 kHz to 1 MHz, and for sediment types between medium silt (grain diameter 25 μm) and coarse sand (700 μm). Published in-situ measurements of R at low frequency (up to about 10 kHz) and...
conference paper 2005
document
Ainslie, M.A. (author), TNO Defensie en Veiligheid (author)
Long-range acoustic propagation in isothermal conditions is considered, involving multiple reflections from the sea surface. If the sea is calm there is almost perfect reflection and hence little loss of acoustic energy or coherence. The effect of wind is to increase propagation loss due to rough surface scattering and the interaction with near...
article 2005
document
Ainslie, M.A. (author), Dybedal, J. (author), Lam, F.P.A. (author), Simons, D.G. (author), Snellen, M. (author), TNO Defensie en Veiligheid (author)
The sensitivity of sound speed to temperature makes it possible to use an echo sounder as a thermometer, provided that the salinity and water depth are known with sufficient precision. Could ‘echothermometry’ – i.e., the use of an echo sounder, or a network of echo sounders, to measure temperature in this way – provide a viable alternative to...
conference paper 2005
document
Boek, W. (author), Ainslie, M.A. (author), TNO Defensie en Veiligheid (author)
A model is presented for simulating bistatic short-range reverberation in shallow water, in order to reproduce reverberation measurements made in the Vestfjorden area (Norway). During these measurements, a low frequency active sonar source was used to transmit short CW signals of frequency 1500 Hz and duration 10 ms. The echoes were received on...
conference paper 2006
document
van Walree, P.A. (author), Ainslie, M.A. (author), Simons, D.G. (author), TNO Defensie en Veiligheid (author)
Echo energies of single-beam echo sounders are inverted for the sediment mean grain size via a combination of theoretical and empirical relationships. In situ measurements of the seafloor mass density have revealed the presence of a thin transition layer between the water and the sediment. Within this layer, which has a thickness of order 1 cm,...
article 2006
document
Lam, F.P.A. (author), Beerens, S.P. (author), Ainslie, M.A. (author), TNO Defensie en Veiligheid (author)
Naval operations in coastal waters are challenging the modelling support in several disciplines. An important instrument for undersea defence in the littoral is the LFAS sonar. To adapt to the local acoustic environment, LFAS sonars can adjust their operation depth to increase the coverage of the sonar. The optimal depth can be determined by a...
conference paper 2006
document
Simons, D.G. (author), Harrison, C.H. (author), van Walree, P.A. (author), Janmaat, J. (author), Ainslie, M.A. (author), TNO Defensie en Veiligheid (author)
Acoustical measurements by single beam echo sounders in the Cleaver Bank area of the North Sea are described. The water depth in the region of interest is about 35 m and the echo sounder frequencies are between 12 and 200 kHz. The data are processed in a number of different ways, each highlighting different features of the seabed. Regions of...
conference paper 2006
document
Ainslie, M.A. (author), TNO Defensie en Veiligheid (author)
Multipath ocean reverberation originating from the seabed in shallow isovelocity water, with particular attention to its information content in the cylindrical spreading and mode stripping regions, is considered. The reverberation is evaluated using Weston's flux integral method, both analytically with various simplifying approximations and...
article 2007
document
Ainslie, M.A. (author), Boek, W. (author), Nielsen, P.L. (author), Harrison, C.H. (author), TNO Defensie en Veiligheid (author)
A measurement of reverberation provides an opportunity to estimate geoacoustic parameters of the seabed by searching the relevant parameter space for a combination of inputs that, when fed into a reverberation model, best matches the measured data. The success of this process relies in part on the accuracy of the reverberation model used. In...
conference paper 2007
Searched for: +
(1 - 20 of 129)

Pages