estimated transmitted sound pressure level please see attached

I need help in:

 

Figuring out the estimated transmitted sound pressure level, SPL using the reference: worker 1 and worker 2, in the last page and i
f possible referring ACGIH Threshold Limit Value (TLV).
Figuring out how to select a barrier material to reduce noise inside the shaping machine. What is the formula that can be used to figure this out?