Except for attenuation of ambulatory noise, is there any acoustic value in practical terms, to install a cork (Portuguese or otherwise) layer, under a wood floor?
I wouldn't think so. Mass is you friend for reducing the escaping sound (and the ambient sound from the other rooms getting into the theater) and Cork is very light weight and pourous.
If you are needing a heavy mass underneath a wood floor, I would strongly concider rubber stall mats (horse stall mats that they sell at farm supply stores). They are 3/4" thick and extremely heavy.
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