Accession Number : AD0785224

Title :   Distributions of Target Strengths and Horizontal Dimensions for Aggregations and Schools of Marine Organisms.

Descriptive Note : Final rept.,

Corporate Author : TRACOR SCIENCES AND SYSTEMS AUSTIN TEX

Personal Author(s) : Larsen,Hugh L.

Report Date : 14 AUG 1974

Pagination or Media Count : 75

Abstract : Recordings of absolute echo levels from marine acoustic targets (schools of pelagic organisms) were analyzed to measure distributions of peak target strengths at two frequencies, 11 kHz and 30 kHz. Since the recordings were not simultaneous, different sets of targets were analyzed at each frequency. At 30 kHz, peak target strengths ranged between - 10 dB and 28 dB with a mean target strength of 18.8 dB. At 11 kHz, the measurements ranged from -25 dB to 11 dB with a mean of 4.2 dB. Distributions of two target horizontal dimensions were also obtained. These dimensions ranged between 5 meters and approximately 400 meters with a mean of approximately 40 meters. Most probable target diameter (highest frequency of occurrence) was approximately 20 meters. A trend toward higher target strengths for larger targets was observed at both frequencies. (Author)

Descriptors :   *Underwater targets, *Marine biology, *Sonar, Target strength, Very low frequency, Fishes, Underwater sound

Subject Categories : Biological Oceanography

Distribution Statement : APPROVED FOR PUBLIC RELEASE