Just some more "afterthoughts" on the subject...I can see the Sauropod tail possibly being used as a defensive weapon by knocking over a predator (using the bulk of the tail, and swinging the body around). I can also see the tail being used to "trip" the predator by use of the distal section wrapping around a predators legs (...perhaps). But for it to use the very tip of the tail in a whiplike fashion would require fairly precise timing and proper distance. Could a Sauropod see that clearly the distance from it`s head to it`s tail? Even if so, wouldn`t it require binocular vision to judge the distance???
As far as producing sound for communication, it would need quite an area of open space to "crack it`s whip". Trees and bushes in the way would not do.....( I can just picture it`s whip getting stuck in a knot around a treetrunk!) Would be hampered when in the water as well. Would have to be out in the open to crack it`s whip.Seems like too many obstacles for a communication device.