I think you will need air flow or it will happen, to help sound proof some blinds I have made and used, we always used the sheet foam from Lowe's or like places, 4x8 sheets and then fit form it tight to walls and ceiling , using construction adhesive to hold it in place! on floors we used carpet and just replaced as needed, always used treated lumber too and deck screws that will last in it!
we always added vents and place small screen over to keep spiders and such out but still have air flow