I have seen cork as sound deadner in older cars (don't remember which one). I think it would make a decent sound barrier, BUT, as mentioned above, it can absorb moisture, so if you car is leaky or has a dripping A/C, this is going to exaserbate (sp) the wet carpet problem. Iwouldn't worry about fire hazard, if the cars catches ablaze, that is not going to make that big of a difference. I would think that the non-organic sound pads would be less expensive than cork, though.