Results from a series of acoustic variability experiments

• Published in: The Journal of the Acoustical Society of America 2002-11, Vol.112 (5_Supplement), p.2308-2308
• Main Authors: Siderius, Martin, Nielsen, Peter, Sellschopp, Jurgen
• Format: Article
• Language: English
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.4808609

A series of experiments were conducted in recent years by the SACLANT Undersea Research Centre to measure the effect of the environment on acoustic propagation. These broadband, shallow water experiments used a moored vertical array with both towed and fixed sound sources. During the fixed experiments the sound source was mounted on a steel frame tower that was resting on the seabed. This design was used to isolate the acoustic fluctuations caused by the environment from those due to source motion. During transmissions extensive measurements of the environment were made including range-depth profiling of the ocean sound speed along the propagation track using a vertically towed CTD (conductivity, temperature, and depth) chain. The seabed types at the sites varied from soft clay (sound speed less than in the water) to a highly reflective sand-gravel (sound speed about 1750 m/s). The temporal fluctuations and spatial structure of the received acoustic signals varied greatly between the sites. This had a big impact on propagation modeling for transmission loss; matched-field processing; and model-based, geo-acoustic inversion. In this paper an overview of these acoustic variability experiments will be described along with results showing the effect of the environment on model-based processing.