Consider a long pipe filled with some newtonian liquid, with piston at both the ends. You push the piston at end A, and observe it at the other end B. How much time does it take for piston at B to move ? Or what is the speed at which this transfer takes place ?

If we consider a perfectly rigid pipe, and a perfectly incompressible liquid (without any dissolved air in it), what speeds can it reach ? Will it break the sound barrier ?