Super Smash Brothers - Cosplaying as each other

When you run at the speed of sound, all you see is darkness anyway.

puts on nerd glasses
I think you mean the speed of light. While moving at the speed of sound, the speed of light relative to you would be indistinguishable from the speed of light relative to you if you were just standing still. So while moving at the speed of sound, you would still be able to see fine.
takes off nerd glasses