What is an Ultra Sonic Test?

What do these numbers mean?  If the material being tested is homogeneous and of consistent integrity (not delaminating or exhibiting voids), then the sonic waves traveling through it will travel uninterrupted at a baseline velocity.  The more “unsound” the material, the slower the sound travels through it.  In cases where voids or cracks occur, the sound wave must find a pathway to travel around the flaw.  Hence higher is better, and lower is worse leading to the color code system above with green being good to excellent, yellow being poor to marginal, and red meaning very poor