Under-Ice Broadband Transient Measurements and Processing

• Main Author: Meredith, Roger W.
• Other Authors: NAVAL OCEANOGRAPHIC AND ATMOSPHERIC RESEARCH LAB STENNIS SPACE CENTER MS
• Format: Text
• Language: English
• Published: 1992
• Subjects: Snow; Ice and Permafrost; Explosions; Acoustics; *SEA ICE; *UNDERWATER EXPLOSIONS; *ACOUSTIC DETECTION; SOURCES; COHERENCE; PATHS; REFLECTION; DEPTH; EXPLOSIVES; FREQUENCY BANDS; ICE; BROADBAND; BACKGROUND; SEPARATION; NOISE; MEAN; HYDROPHONES; OCEANS; RAY TRACING; UNDERWATER ACOUSTICS; ACOUSTIC VELOCITY; ANTISUBMARINE WARFARE; BACKGROUND NOISE; TRAVEL TIME; PROPAGATION; ARCTIC OCEAN; FREQUENCY; TRANSIENTS; PE62435N; WUDN496433; Arctic; Arctic Ocean; Ice; ice pack; permafrost; Sea ice
• Online Access: http://www.dtic.mil/docs/citations/ADA248609; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA248609

This report examines the horizontal spatial coherence of broadband acoustic energy in the frequency range 100-1200 Hz from explosive sources under the ice pack. The data were recorded on four hydrophone pairs with a nominal sensor separation of 370 m from source ranges from 3 to 25 km. Mean-square coherence is computed separately for the direct and ice-reflected propagation paths, and octave band frequency averaging reduces variability inherent in the coherence estimation associated with explosive acoustic sources. Coherence varies significantly with sensor depth, range, and frequency. Background noise coherence is also examined briefly. Changes in coherence because of under-ice reflection are smallest for the 100-200 Hz octave band, but the change may be as high as 50% for the higher frequency bands.