Reception at Ascension Island, South Atlantic, of the transmissions from the Heard Island Feasibility Test.
Advanced Search
Select up to three search categories and corresponding keywords using the fields to the right. Refer to the Help section for more detailed instructions.
 
 
i


Reception at Ascension Island, South Atlantic, of the transmissions from the Heard Island Feasibility Test.
Filetype[PDF-38.98 MB]


This document cannot be previewed automatically as it exceeds 5 MB
Please click the thumbnail image to view the document.
Reception at Ascension Island, South Atlantic, of the transmissions from the Heard Island Feasibility Test.
Details:
  • Description:
    The objective of the Heard Island Feasibility Test was to ensonify the global ocean with a single source to determine the feasibility of acoustically measuring the extent of ocean warming. Underwater acoustic signals were transmitted from a ship in the southern Indian Ocean and monitored at listening stations throughout the world. At Ascension Island, about 9,200 km from the source ship, all transmissions from the Heard Island Feasibility Test were recorded on at least eight hydrophones and, for many transmissions, on 11 hydrophones. The depths of most of these hydrophones are near the depth of the sound channel axis but some are considerably deeper. All are bottom mounted. Signal-to-noise ratios were found to be surprisingly high. Averaged over the CW transmissions and in a 1 Hz band, signal-to-noise ratios for the axial hydrophones south of the island range from about 19 to 30 db, adjusted to a source level of 220 db (referenced to 1 µPa at 1 m). The average signal-to-noise ratio for a hydrophone at a depth approximately 0.8 km below the axis is about 16 db, suggesting acoustic energy was not restricted to a narrow interval in depth centered about the sound channel axis. The travel time of the earliest arrival was found to be about 1 h, 44 min, 17 s. A late, reverberative signal was observed for at least 22 min after termination of the direct signal. An unexpected combination of phase stability and amplitude variability was observed in the received signals. Continuing analysis of the Ascension data set is likely to provide considerable information about the characteristics of acoustic signals that have propagated global distances.
  • Document Type:
  • Place as Subject:
  • Rights Information:
    Public Domain
  • Main Document Checksum:
  • File Type:
  • Supporting Files:
    No Additional Files
No Related Documents.

You May Also Like: