Acoustic Propagation in Turbulent Layers

The objective of this work was to determine the extent to which acoustic propagation varies in the vicinity of topographic features where the flow oscillates between laminar and turbulent states. Since these topographic features are ubiquitous in coastal areas, the results will impact ACOMMS performance in these areas. In a recent experiment by Mourn and Nash, oceanographic measurements were made around a small bank off the western continental shelf (Fig. 1). Temperature, salinity, and turbulent dissipation rate measurements were obtained from this experiment and broadband (9-llkHz) acoustic simulations done to determine the impact of the turbulent sound speed field on acoustic propagation. Acoustic simulations show an overall increase in transmission loss of about 10-15 dB within the 10-11 KHz band. This corresponds to the times where intense turbulence occurs. The transmission loss correlates well with the turbulent dissipation rate.