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Recording of "Alexander's Acres," an example of reflection patterns.

Recording of "Alexander's Acres," an example of reflection patterns.
Recording of "Alexander's Acres," an example of reflection patterns.
Recording of "Alexander's Acres," an example of reflection patterns.
Recording of "Alexander's Acres," an example of reflection patterns.
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Recording of "Alexander's Acres," an example of reflection patterns.
Illustration
01/01/1960
com/cullen/DB slopewater.jpg
Chart courtesy of Richard Backus.
Date is approximate.
Image Of the Day caption:
The marks on this figure are acoustic traces, the visual representations of underwater sounds recorded at sea sometime around 1960. Sounds such as these interfered with the U.S. Navy's ability to detect enemy submarines but at the time, the origin of these underwater noises was unknown. WHOI geophysicist John Brackett Hersey hired marine biologist Richard Backus to help figure out who or what was making them. During a dive in the submersible Alvin in 1967, Backus discovered their source: large schools of the common midwater lanternfish Ceratoscopelus maderensis.
Caption from Down to the Sea for Science, pg. 113:
Acoustic traces like these were the object of many years' study by the geophysics group. In an early interdisciplinary move, group leader Brackett Hersey hired biologist Dick Backus for these investigations. The figure shows a recording (circa 1960) of "Alexander's Acres," one among many reflection patterns that plagued naval personnel looking for submarines. ("Alexander" was Lieutenant Sidney Alexander, skipper of the USCG Cutter Yamacraw, used by the geophysics group in 1957 and 1958.) Backus ultimately was able to positively identify "Alexander's" fish when he could see them from Alvin during a dive in 1967. They proved to be large schools of 2.5 inch (63-millimeter) myctophid or lanternfish, Ceratoscopelus maderensis.
Photo courtesy of WHOI Archives
© Woods Hole Oceanographic Institution
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