Looks like no one added any tags here yet for you.
White → Black
Metal>Bone>Soft Tissue/Fluid>Fat>Gas
Air = 331m/s
Fat = 1450m/s
Fluid & soft tissue = 1540m/s
Bone = 4080m/s
Higher frequency = higher resolution = shallower depth
Lower frequency = lower resolution = deeper depth
White → Black
Gas>Bone>Tissue>Fluid