GLORIA

GEOMAR Library Ocean Research Information Access

X

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1990-1994  (6)
Material
Publisher
Person/Organisation
Language
Years
  • 1990-1994  (6)
Year
FID
Subjects(RVK)
  • 1
    Online Resource
    Online Resource
    HIFE signal processing results.
    Acoustical Society of America (ASA) ; 1991
    In:  The Journal of the Acoustical Society of America Vol. 90, No. 4_Supplement ( 1991-10-01), p. 2348-2348
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 90, No. 4_Supplement ( 1991-10-01), p. 2348-2348
    Abstract: The most remarkable feature of the HIFE receptions is their phase stability in both time and frequency. Examples include (1) tracking of the peak-energy bin of FFT’s, (2) refinement of the carrier estimate to a precision adequate to estimate the transmission launch angle, and the small residual phase deviation track over a full hour, (3) the small phase swing of the integrated autocorrelation phase (IAP1) over one full hour, (4) the phase stability of arrivals, after removal of the broadband phase deviations measured by IAP1, and (5) comparison of the measured distributions of amplitude and phase of the individual frequency lines and individual time arrivals. The implications for phase coherent signal processing, in particular for more frequent transmissions in fixed–fixed tomography and for Doppler utilization in moving source tomography, will be discussed. Last but not least, the utilization of the arrival phase along the several sheets of propagating timefronts by passive broadband channel matching will be discussed.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.402147
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1991
    detail.hit.zdb_id: 1461063-2
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 2
    Online Resource
    Online Resource
    HIFE signals and general results.
    Acoustical Society of America (ASA) ; 1991
    In:  The Journal of the Acoustical Society of America Vol. 90, No. 4_Supplement ( 1991-10-01), p. 2329-2329
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 90, No. 4_Supplement ( 1991-10-01), p. 2329-2329
    Abstract: HIFE transmitted for 28 full hours and 8 half hours, repeating the same signal continuously for each transmission. HIFE had a repertoire of cw, Pentaline, and four different phase-coded time-resolving signals based on m sequences. The several purposes of each signal will be explained. Receptions were processed on line at 14 sites at ranges of 200 to 18 000 km; to date, the digital tapes from 8 sites have been processed at CSPL. The feasibility questions concerning power, stability, time resolution, and dispersion were answered, and a thorough study of the receptions begun. Examples of the on-line processing and selected frequency domain and travel-time-domain time series will be presented and discussed. An extraordinary look at the phase stability of the propagation was revealed through comparison of (1) the diagonal ship surge deviation from a uniform path measured at the transmitter, and (2) the integrated autocorrelation phase (IAP1) after constant Doppler correction measured at a 9000-km distant receiver.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.402237
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1991
    detail.hit.zdb_id: 1461063-2
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 3
    Online Resource
    Online Resource
    Integrated autocorrelation phase at one period lag
    Acoustical Society of America (ASA) ; 1994
    In:  The Journal of the Acoustical Society of America Vol. 96, No. 4 ( 1994-10-01), p. 2353-2356
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 96, No. 4 ( 1994-10-01), p. 2353-2356
    Abstract: Various types of phase measurements have been introduced into ocean acoustic measurements since the early 1960s, many utilizing the increased precision possible with digital processing. These are usually considered natural and basic by their developers, but are frequently misunderstood and mistrusted by those they were designed to benefit. This paper explains a recent phase technique which was used in the Heard Island Feasibility Test data analysis of the Ascension Island receptions. It revealed that the common phase fluctuations of the wideband M-sequence receptions were not random, but were caused by minor deviations of the source ship track 9200 km away.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.410107
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1994
    detail.hit.zdb_id: 1461063-2
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 4
    Online Resource
    Online Resource
    Signals, signal processing, and general results
    Acoustical Society of America (ASA) ; 1994
    In:  The Journal of the Acoustical Society of America Vol. 96, No. 4 ( 1994-10-01), p. 2343-2352
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 96, No. 4 ( 1994-10-01), p. 2343-2352
    Abstract: Acoustic path lengths in the Heard Island Feasibility Test ranged from under 1 Mm to 18 Mm (1 Mm is 1000 km). The signal set consisted of three basic waveforms: cw, pentaline, and M-sequence-modulated carrier. This set offered the opportunity for successful measurements given the large uncertainty in prior estimates of propagation loss, stability, and arrival spread. Receivers ranged from simple sonobuoy systems to elaborate horizontal and vertical arrays. International collaborators acquired data at a variety of sites worldwide. The resulting data has been collected and subjected to a summary form of frequency domain processing. Variations in the recorded spectral phases are largely the result of nonuniformity in the speed of the source ship as determined by GPS comparison. Time domain processing has shown that at all ranges the receptions exhibit exceptional stability.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.410106
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1994
    detail.hit.zdb_id: 1461063-2
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 5
    Online Resource
    Online Resource
    The sensitivity of global acoustic measurements to climate change
    Acoustical Society of America (ASA) ; 1994
    In:  The Journal of the Acoustical Society of America Vol. 95, No. 5_Supplement ( 1994-05-01), p. 2879-2880
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 95, No. 5_Supplement ( 1994-05-01), p. 2879-2880
    Abstract: An ongoing experiment, Acoustic thermometry of ocean climate (ATOC), measures the integrated heat content of path through an ocean basin by recording the travel time perturbations of low-frequency sound waves. Anthropogenic CO2 in the atmosphere is expected to heat the oceans. Many physical processes affect the travel time signal in addition to the greenhouse signal. A partial list includes: internal waves, tides, mesoscale eddies, seasonal and interannual variability. A relevant question is: What is the signal-to-noise ratio of the CO2 warming signal versus the ambient signal? A synthetic experiment was therefore run to estimate the acoustic signature of the warming signal. Two coupled ocean-atmosphere general circulation models were run with no CO2 increase and with CO2 doubling. The GCM output was then used as an input to an acoustic propagation model. The acoustic time series can then be analyzed for climatic trends. The control run is used to estimate the ambient noise processes on long term scales. Shorter time scale processes can also be quantified and signal-to-noise ratios can then be constructed. The spatial properties of the CO2 signal are nonuniform and therefore maps of the signal strength are also constructed.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.409428
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1994
    detail.hit.zdb_id: 1461063-2
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 6
    Online Resource
    Online Resource
    A spectral method for calculation of ocean acoustic normal modes using Chebyshev polynomials
    Acoustical Society of America (ASA) ; 1993
    In:  The Journal of the Acoustical Society of America Vol. 94, No. 3_Supplement ( 1993-09-01), p. 1785-1785
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 94, No. 3_Supplement ( 1993-09-01), p. 1785-1785
    Abstract: A new method employing Chebyshev polynomials to calculate the underwater acoustic normal mode equation was developed. The method is a spectral approach using Chebyshev polynomials as basis functions. This expansion has the advantage of being a particularly efficient and accurate representation of the normal modes (especially of the lower order) since they give an exceedingly good representation of narrow boundary layers such as the sound-speed profile that can undergo rapid changes near the surface. This representation reduces the size of the eigenvalue problem to be solved. Since the CPU time scales with N3, where N is the size of the matrix, any size reduction is an advantage computationally. This approach has a significant speed advantage over finite difference methods without sacrificing accuracy. A Chebyshev representation is usually remarkably close to the minimax polynomial that minimizes the maximum error implying high accuracy. Chebyshev polynomials are also useful for the calculation of quantities involving the integral of the mode function, such as modal group velocity, loss, and coupling coefficient matrices in non-adiabatic propagation environments. These quantities can be calculated easily and accurately given their spectral representations without introducing any further numerical error.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.407947
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1993
    detail.hit.zdb_id: 1461063-2
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...