What are the properties of the best barriers for general outdoor noise?
Number of reflective panels
How much does the number of panels affect STC (sound transmission class rating)? Many sources claim that removing drywall layers can improve STC.
d = drywall
s = studs
f = fiberglass
a = air space
They claim assembly 2 has a higher STC than assembly 1.
I heard they help between reflective panels. They can't be used in the middle of a window because they block the view.
High ρₛ (mass / area) and low stiffness is best for 1 panel.
Is there a benefit to using a variety of materials?
Reducing coincidence effect
I think this has to do with the relationship panels have with each other, ρₛ, and stiffness.
For a simplified version, what panel thickness ratio is best given they're the same material?