RELATIVE INFLUENCES OF VARIOUS ENVIRONMENTAL FACTORS ON 50-1000 HZ SOUND PROPAGATION IN SHELF AND SLOPE AREAS

摘要

Within a given continental shelf or slope area acoustic propagation effects from many aspects of the environment sum to give the resultant total environmental effect on sound propagation. Signal parameters influenced by the environment include signal strength (transmission loss), vertical coherence scale, horizontal coherence scale, temporal coherence scale, and further signal details not measured by coherence scales, all as functions of frequency. Environmental (oceanographic) factors include but are not limited to bathymetric slope, episodic high-amplitude internal waves, continuous low-amplitude internal waves, seafloor attenuation, fronts, currents, source depth, and receiver depth. The effects of each of these environmental factors may be investigated individually with simulations or with specialized field experiments, but the results often can't be generalized because of first-order differences between regions. In many situations the various factors do not act independently, but are coupled, and not only do the individual parameters vary but their interactions may also change. An example from our previous work is the altered influence of mode-stripping (bottom interaction) in shallow water when high-amplitude internal waves are either present or absent. This effect is sensitive to source depth, bottom parameters, and wave parameters. This example and other simulated examples of differing dominant parameters at selected locations will be presented and compared with acoustic experiment data.