Propagation of Sound Generated on the Ice Surface into Water

• Main Authors: Francois, R. E., Wen, T.
• Other Authors: WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB
• Format: Text
• Language: English
• Published: 1989
• Subjects: Acoustics; *AMBIENT NOISE; *SEA ICE; *CONTAMINATION; *ACOUSTIC MEASUREMENT; *NOISE POLLUTION; *UNDERWATER ACOUSTICS; DEPTH; EMPLACEMENT; SOUND TRANSMISSION; SHORT RANGE(DISTANCE); LOSSES; ACOUSTIC ABSORPTION; HYDROPHONES; ACOUSTIC FIELDS; SHADOWS; ARCTIC REGIONS; FACILITIES; ACOUSTIC WAVES; MODELS; MILITARY FACILITIES; ACOUSTIC REFRACTION; SIMULATION; SOURCES; PE62435N; WUDN496433; Arctic; Sea ice
• Online Access: http://www.dtic.mil/docs/citations/ADA213583; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA213583

One of the difficulties in taking underwater acoustic measurements at arctic ice camps is avoiding contamination of the measurements with camp- generated noise. To minimize this problem, investigators sometimes use a surface-laid cable system to place hydrophones well away from the camp. But how far from an ice camp must hydrophones be to ensure that camp-generated high- frequency interference (>1 kHz) is negligible? To answer this question, simulated camp noise was propagated from a source on top of the ice into the water below. Short-range measurements were then taken to locate the shadow zone under the ice where the acoustic energy from the source is negligible compared with the ambient noise field. This shadow zone was compared with sound propagation models that accounted for the refraction and absorption losses in the sea ice and in the water below. Inputs to the models were then adjusted to simulate different environmental conditions and longer ranges. Finally, conservative formulae were developed for determining the range and depth of hydrophone placement for a given reduction in the sound level from the source on the surface.