They are fundamentally different "barriers". Sound barrier is just a misnomer for the development of a shock front (Mach cone) by an object going faster than sound. Light "barrier" is an intrinsic property of spacetime. In fact the essence of relativity is that there *is* no "light shock front" in vacuo. (There is a phenomenon called Cerenkov radiation that can be qualitatively understood as a light shock front in a material medium in which the effective SOL is less than C.)

[link|http://dept.physics.upenn.edu/balloon/cerenkov_radiation.html|http://dept.physics....ov_radiation.html]

In vacuo, a Mach cone for light is in principle impossible. Can't overstate this - nothing in our physical world will ever go faster than C. These facts are not open to any doubt, and are constantly verified in particle accelerators and cosmic ray studies.