• Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Journal of the Acoustical Society of America

SECTION LISTING

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue

Dec 1986

Volume 80, Issue S1, pp. S1-S128

Return to All Sections
back to top
RSS Feeds
back to top Session NN. Underwater Acoustics VII: Remote Sensing and Underwater Acoustics, Part 1
Invited Papers
FREE

The application of present and future satellite remote sensors to oceanographic acoustics (A)

R. A. Shuchman

J. Acoust. Soc. Am. Volume 80, Issue S1, pp. S81-S81 (1986); (1 page)

Online Publication Date: 13 Aug 2005

Full Text: | Download PDF

Show Abstract
An ensemble of active and passive satellite remote sensors are presently operating or will be launched in the near future that provide high resolution detailed oceanographic information on a synoptic scale. These sensors operate in the visible, infrared, and microwave region of the electromagnetic spectrum and include the NOAA 7/8 (TIROS), NIMBUS‐7, LANDSAT, SPOT, and GEOS satellites presently in orbit as well as the planned ESA ERS‐1, NROSS, TOPEX, RADARSAT, and JERS‐1 satellite launches. The information provided by these satellites includes not only ocean surface and air/sea environmental information such as wind speed and direction, gravity wave spectral estimates, surface water height, salinity, temperature, and water vapor content, but also information about the interior of the water column (i.e., fronts, upwelling, and internal waves). Additional information about the ice‐covered ocean can also be provided by these satellite data. The sea ice information includes; ice edge location, ice concentration, floe size distributions, ice type, and ice kinematics. The merging of remote sensing data with acoustical data can potentially provide new insight into understanding the interior structure of the ocean. The use of acoustical data to aid in the interpretation of remote sensing oceanographic data can in turn increase the use of the satellite information.
FREE

Satellite impact on environmental acoustics (A)

S. A. Piacsek, F. Jensen, and P. Van Meurs

J. Acoust. Soc. Am. Volume 80, Issue S1, pp. S81-S81 (1986); (1 page)

Online Publication Date: 13 Aug 2005

Full Text: | Download PDF

Show Abstract
The continuous surveillance of atmospheric and oceanic conditions at the sea surface by remote sensing platforms can be exploited to improve acoustic propagation prediction. This improvement is especially important in areas where surface observations are not usually taken or are difficult to take, e.g., in oceanic areas off the main shipping routes or under stormy weather patterns. It has been recently shown that both the climatology of the water mass, as well as the analyzed and/or predicted atmospheric surface fluxes can contain significant errors that are larger than those associated with the remotely sensed signals. The purpose of this paper is to illustrate quantitatively the improvement in the prediction of the acoustic environment and propagation due to remote sensing in such situations by three examples. The first two will use a 1‐D mixed‐layer model coupled to a range‐independent acoustic model to study the impact of joint scatterometer/IR observations on propagation in surface ducts. Both a situation where mechanical stirring due to the wind or where convective stirring due to strong surface cooling is dominant are investigated. The third example will study the improvement in the description of the vertical structure and the horizontal position of an oceanic front, and the corresponding acoustic propagation patterns, due to combined altimeter/IR observations. This study will use a 2‐D ocean model coupled to a range‐dependent acoustic model.
FREE

Ocean sensing and modeling as a basis for acoustic prediction (A)

Jerald W. Caruthers, Jim L. Mitchell, Theodore J. Bennett, Jr., George E. Kerr, Paul W. May, and P. W. deWitt

J. Acoust. Soc. Am. Volume 80, Issue S1, pp. S81-S81 (1986); (1 page)

Online Publication Date: 13 Aug 2005

Full Text: | Download PDF

Show Abstract
Several ongoing projects at the Naval Ocean Research and Development Activity (NORDA) form a vertical program for the development of ocean sensing and modeling aimed at supporting acoustic predictions. These projects cover the spectrum from basic research to advanced development. This paper reviews an emerging philosophy for the integration of these several disciplines and presents an example of the application of a part of that philosophy. The example provides comparisons among acoustic propagation runs for various representations of a 600‐km‐long, vertical section across the Gulf Stream in the northwest Atlantic Ocean. These representations include (1) a dataset of 700‐m XBT's merged with historic profiles to the ocean bottom and spaced at 20 km; (2) an optimally interpolated set of profiles spaced at 5 km; (3) a dataset developed from altimetric data spaced at 5 km; and (4) a single point profile. [Work supported by NORDA, ONT, and the Naval Oceanography Program.]
FREE

Ocean acoustic tomography and acoustic propagation (A)

R. C. Spindel and P. F. Worcester

J. Acoust. Soc. Am. Volume 80, Issue S1, pp. S82-S82 (1986); (1 page)

Online Publication Date: 13 Aug 2005

Full Text: | Download PDF

Show Abstract
Ocean acoustic tomography is a method for remotely sensing deterministic and stochastic variations in the ocean sound speed field. The fundamental tomographic measurement is sound speed, and therefore tomography directly provides acoustic propagation models with this essential, first‐order, environmental information. In one form or another the various sound propagation codes rely on sound speed data in either 2‐, 3‐ or 4‐dimensional form. Experiments have shown that both mean and range‐varying sound speed data can be obtained using tomography, and that when appropriate assumptions are made about the known horizontal and vertical covariance structure of the ocean, these data are spatially continuous. Thus it is not necessary to choose an interpolation scheme for discrete profiles that may be mathematically sensible, but physically less meaningful. Further, since the tomographic measurement itself uses propagating acoustic waves, it affords an opportunity to obtain simultaneously selected sound propagation parameters. We discuss these and other aspects of tomographic remote sensing and its application to acoustic propagation.
Contributed Papers
FREE

Multiple receivers in single vertical slice ocean acoustic tomography experiments (A)

Bruce M. Howe

J. Acoust. Soc. Am. Volume 80, Issue S1, pp. S82-S82 (1986); (1 page)

Online Publication Date: 13 Aug 2005

Full Text: | Download PDF

Show Abstract
Will additional receivers widely spaced in the vertical on each mooring of an (x,z) tomographic experiment improve the range‐dependent estimates of the sound speed and water velocity fields? Numerical simulations were performed to answer this question. For a 300‐km range, additional receivers reduce the error variance of the estimated perturbation sound‐speed field δc(x,z) a factor of 3 (as compared with the case with single hydrophones) to 3% of the a priori variance (0.5 m/s or ∼0.1°C rms). For a 1000‐km range, range‐dependent features are only marginally resolved, even with additional recovers and optimistic data error levels. Range dependence in the velocity u(x,z) is unresolved in all cases.
FREE

Distributed acoustical assimilation in the equatorial Pacific Ocean (A)

Thomas L. Clarke and John R. Proni

J. Acoust. Soc. Am. Volume 80, Issue S1, pp. S82-S82 (1986); (1 page)

Online Publication Date: 13 Aug 2005

Full Text: | Download PDF

Show Abstract
The possibility of using a dynamical‐model‐based equatorial ocean data assimilation technique as the basis for tomographic inversion is explored. In the equatorial Pacific relatively few ray paths come near the surface causing difficulty for most inversion techniques. A data assimilation technique being developed at the Physical Oceanography Division of AOML/NOAA [Thacker and Long, in preparation] uses a dynamical approach that can provide coupling between the deep conditions that are directly sensed by the acoustics, and the near surface events that are of direct climatic significance. The model decomposes temperature variability into dynamical modes identifiable with Kelvin and Rossby waves; the sensitivity of individual ray‐path travel times to the modes is used as the basis for the inversion. The acoustic data is assimilated with other ocean measurements by using a LaGrange multiplier approach constrained by the dynamics. Ray tracing results using equatorial Pacific temperature data are presented which show the promise of dynamical‐model assimilation based tomographic inversion as a means of detecting near surface temperature anomalies in the equatorial Pacific.
FREE

Ocean and satellite data sets for acoustical modeling (A)

Jim L. Mitchell, Zachariah R. Hallock, and William J. Teague

J. Acoust. Soc. Am. Volume 80, Issue S1, pp. S82-S82 (1986); (1 page)

Online Publication Date: 13 Aug 2005

Full Text: | Download PDF

Show Abstract
Quasisynoptic ocean data sets consisting of thermal sections of data collected from deep (800‐m) Airborne Expendable Bathythermographs (AXBTs) and sea surface topography measured by overflights of the U.S. Navy GEOSAT altimetric satellite are presented and analyzed. These data, collected as part of the NW Atlantic Regional Energetics Experiment (REX) during August 1985, cover a significant portion of the Gulf Stream front from approximately 57°W to 68°W including three warm meanders and the intervening two cold meanders. Additionally, two warm core rings and one Sargasso cold core ring are included in the region mapped during the six‐day period of the AXBT survey. Using climatological regression between the dynamic thickness (0/3000 dbar) and isotherm depth, these in situ thermal data are compared with sea surface topography as measured by the GEOSAT altimeter. These data sets form the basis of the range‐dependent acoustical model runs discussed in detail in a jointly submitted invited paper NN3 in this session.
FREE

Estimating sea surface spectra with acoustic tomography (A)

James H. Miller, Ching‐Sang Chiu, and James F. Lynch

J. Acoust. Soc. Am. Volume 80, Issue S1, pp. S82-S82 (1986); (1 page)

Online Publication Date: 13 Aug 2005

Full Text: | Download PDF

Show Abstract
A technique for estimating space‐ and time‐varying sea surface spectra using acoustic tomography is described. The technique uses acoustic (mode and/or ray) phase or travel time perturbations as data for the inversions. The inverse problems for spatially homogeneous and spatially nonhomogeneous frequency‐directional wave spectra are discussed. Resolution and accuracy of the technique are addressed. Results of inversions of synthetic data are presented as well as an application of this technique to data taken during the MIZEX '84 preliminary tomography experiment. Directions of future research are indicated.
FREE

Sound‐speed profile inversion in the ocean (A)

Linda Boden and John DeSanto

J. Acoust. Soc. Am. Volume 80, Issue S1, pp. S82-S82 (1986); (1 page)

Online Publication Date: 13 Aug 2005

Full Text: | Download PDF

Show Abstract
For sound‐speed profiles which vary only in depth, a method has been developed whereby the scattered field data in frequency (or k‐space) can be related to the sound‐speed profile correction (from an assumed profile guess input) as a quasi‐Fourier transform pair. The inversion is straight‐forward using this Fourier relationship. The method uses a Fourier‐Bessel representation of the acoustic field, a Born approximation on the depth dependent part of the Green's function, a WKB representation for the wave functions and asymptotics and linearizations to derive the transform pair. In spite of all the approximations, good results are obtained for profile recovery using synthetically generated data.
FREE

Application of discrete linearized inversion to the sofar inverse problem (A)

Peter Kaczkowski and John A. DeSanto

J. Acoust. Soc. Am. Volume 80, Issue S1, pp. S83-S83 (1986); (1 page)

Online Publication Date: 13 Aug 2005

Full Text: | Download PDF

Show Abstract
Inversion for the one‐dimensional sound‐speed profile in the sofar waveguide is performed using damped least squares (Marquardt‐Levenberg algorithm). The study uses the split‐step parabolic equation method to solve for the synthetic acoustic pressure field in the ocean. Data for the inversion are also provided by the same model, and the robustness of this technique is investigated using different samples of the sound field: horizontal and vertical arrays of varying length and, single point data of varying bandwidth. The parameter resolution matrix and the singular value decomposition of the matrix of partial derivatives lend insight into the inversion and provide quantitative measures of the relative merit of different experimental configurations, and this will be discussed.
FREE

High‐resolution time of arrival estimation via linear prediction (A)

Ivars P. Kirsteins

J. Acoust. Soc. Am. Volume 80, Issue S1, pp. S83-S83 (1986); (1 page)

Online Publication Date: 13 Aug 2005

Full Text: | Download PDF

Show Abstract
A new method is presented for estimating the arrival times of overlapping signal pulses that are separated by less than the duration of the signal autocorrelation function. The method is based on the observation that if the signal has a flat band‐limited spectrum, then the maximum‐likelihood estimator for the time of arrivals can be approximately transformed into an equivalent high‐resolution exponential parameter estimation problem. Then, an improved linear prediction algorithm [D. W. Tufts and R. Kumaresan, Proc. IEEE 70, 975–989 (1982)] for high resolution exponential parameter estimation is used to estimate the time of arrivals. The proposed method is computer simulated for two linear FM sweep signal pulses at various separations and signal‐to‐noise ratios. The simulation results are compared to the Cramer‐Rao lower bound (CRLB). These results indicate performance close to the CRLB over a reasonable range of pulse separation and signal‐to‐noise ratios.
Return to All Sections
Close

Home Publications Meetings Contact ASA Site Map Back to Top

Copyright © Acoustical Society of America

close