The answer is this. This has been proven by investigation of particals called muons. The neat thing about muons is that they exist for an extrememly short time. So short, infact,that they should only be able to travel a few hundred yards, even though they are at relativistic velocities. This is called the Lorentz effect.
Distance is a function of velocity.
Think about it. We use terms like miles per hour or meters per second. What we really mean is that velocity is a relationship between time and space. They are comepletely different. The sound barrier is a mechanical barrier that arises do to gas dynamics, and chemical kinetics.