Five of the beaked whales survived and were pushed back to sea. The other five died, and were examined by NOAA Fisheries to determine the cause of death. All had hemorrhages in or around the ears. Apparently, the animals died from actually stranding on the beach. Surface ducts are natural phenomena that occur in early spring, and essentially contain sound in a surface layer of the ocean.
Sound travels further within the duct than at greater depths.
This concentration of sound may have injured the whales, and caused disequilibrium or disorientation. The Navy, ever circumspect, says it will reassess its use of sonars during peacetime training if further research shows that mid-range frequency tactical sonars can injure marine mammals. We don't know much about the effect of noise on marine mammals and sea turtles. We do know that the sounds in the ocean are increasing, largely due to shipping, seismic exploration, drilling and sonar. We also know that at about 180 decibels, sound causes bruises in human lung tissue.