thanks Rudeboy & Foxpro!! Exactly what I want to see.
Rudeboy, what happens from 400-900hz. Looks like there's no coverage at all. The vinyl layer of LLP can block sound <400hz? Or could it be your system/rig resonance frequency? From Foxpro's numbers, it should a steady rise in Loss at frequency increases.
The foam makes a huge difference from 1khz and up!
Not to take this too far in a direction that seems to piss a lot of people off, but the barrier/foam composite isn't itself a double wall barrier. If you put the layer of MLV in direct contact with the sheet metal substrate you are basically doubling the mass of the first barrier - the steel substrate. The foam layer makes it a double wall because there is space between wall 1 - the substrate and wall 2 - the MLV.Something like LLP is technically a double wall barrier.