Accession Number : ADA138161

Title :   TRISTEN/FRAM IV CW (Continuous Wave) Spatial Coherence and Temporal Stability.

Descriptive Note : Technical document,

Corporate Author : NAVAL UNDERWATER SYSTEMS CENTER NEW LONDON CT NEW LONDON LAB

Personal Author(s) : DiNapoli,F R ; Nielsen,R ; Potter,D ; Stocklin,P L

PDF Url : ADA138161

Report Date : 01 Feb 1984

Pagination or Media Count : 27

Abstract : The TRISTEN-82/FRAM IV experiment was a multifacted experiment investigating acoustics in the Arctic. This paper focuses on the spatial coherence and temporal (frequency) stability of acoustic signals transmitted and received between fixed ice camps separated by approximately 130 nmi. A high powered, low frequency (NUSC HLF-3 Arctic) hydroacoustic source transmitted stable CW tones of 1 hour or more at various frequencies from 5 to 200 Hz during April 1982. These signals were received on an X-shaped array having an aperture of 1200 m on each leg. The array was operated by the Massachusettes Institute of Technology and the Woods Hole Oceanographic Institution. The spatial coherence of frequencies below 100 Hz, both broadside and endfire to the source, were found from normalized sensor pair cross correlation, corrected for signal-to-noise ratio. Total and 3 dB down received signal bandwidths were found using complex demodulation and FFT with a resolution to a fraction of mHz, followed by cumulative energy analysis in the frequency domain. The major conclusion is that the Arctic is a very stable environment for low frequency acoustic signals. (Author)

Descriptors :   *Acoustic signals, Extremely low frequency, Continuous waves, Arctic regions, Stability, Coherence, Spatial distribution, Signal processing, Demodulation, Hydrophones

Subject Categories : Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE