| Popis: |
A method of detecting oil spills in ice-covered lakes and seas, by observing changes in underwater acoustic reverberation time, had earlier been proposed; testing in a small tank environment showed it to hold some promise. Work now continues to improve the method, to further validate it, and to extend it to large bodies of water. The current work carries such scale testing further, establishing, by hypothesis testing, the level of confidence with which the presence of an oil layer underlying the ice can be discerned. Moreover, it expands the study to full scale experimentation in lakes and seas, including a portion of the Great Lakes across which a pipeline lies. These experiments seek to determine representative reverberation times (albeit without oil contamination, for obvious ethical reasons), and to explore whether natural impulsive sounds from ice fissuring may serve as a basis for passive hydroacoustic monitoring. The experiments at both scales are mutually complementary; while the tank tests serve to more rigorously validate that reverberation time is measurably affected by an oil layer, the lake-scale tests suggest those frequency bands an eventual passive monitoring using naturally arising sound would actually use, and establish the “control case” (oil-free) reverberation times. |
