Sound proofing floor

I wish I could remember what it was; I was watching some YouTube video on room treatment and the guy was talking about just that very thing; was it creosote? Or am I just thinking of Monty Python? 

We used a rubber membrane to help cut the trnasmission of sound through a concrete black wall at school between the dance studio and the recording studio.  It really cut the sound down but it may only be a wall treatment. can't remember the brand