Sounbloc??

[HBGuy]

I kid you not.  It's called Greenfield Sounbloc underlayment.  Has anyone heard of it?
I wonder if it's a knockoff of the Pergo Soundblock(TM) underlayment. 

[Randy S]

I have not heard of that product and I couldn't find any reference on the internet. I really does not make that much of a difference if the ceiling is not decoupled on channel. you are still applying 100% surface contact....the principle of decoupling is to break 90%-95% of surface connection to reduce impact transmission. Your overall results will be determined by the mass of the assembly and number of direct connections (pathways) sound and vibration will travel.