Accession Number : AD0708684

Title :   AN EXPERIMENT ON ACOUSTIC REFLECTION FROM THE SEA SURFACE.

Descriptive Note : Final rept.,

Corporate Author : NAVAL RESEARCH LAB WASHINGTON D C

Personal Author(s) : Ferris,Raymond H. ; Kuperman,William A.

Report Date : 28 MAY 1970

Pagination or Media Count : 18

Abstract : An experiment on underwater acoustic relfection from the ocean's surface was conducted in a water depth of 32 m by utilizing an omnidirectional, 3.5-kHz fixed source at a submerged depth of 16 m. Two-cycle pulses at a repetition rate of 10 pulses per second were received on a hydrophone suspended at a depth of 10.7 m from a small boat. Underwater grazing angles ranged from 15 to 40 degrees. Surface reflection loss was observed to vary over a range of approximately 20 dB with periods closely associated with the predominant water wave periods. Surface reflection gains of up to 5 dB occurred frequently. The average loss ranged from 1 dB at a grazing angle of 15 degrees to 4 dB at an angle of 40 degrees, with only a slight dependence on direction of propagation relative to the direction of the sea. Signals propagated via the surface-reflected path, when correlated with signals propagated via the direct path, exhibited an average peak value of normalized cross correlation of 0.95. (Author)

Descriptors :   (*UNDERWATER SOUND, REFLECTION), SONAR SIGNALS, INTERFACES, HYDROPHONES, SONAR EQUIPMENT, CORRELATION TECHNIQUES, DEPTH FINDING, SCATTERING, VERY LOW FREQUENCY

Subject Categories : Physical and Dynamic Oceanography
      Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE