There was/is an automotive spray product called "Noisekiller Blue" that I always wanted to try; designed for stereo installation deadening, apparently a very light thin foam, for a similar effect to the asphalt sheets without the weight and sticky mess. (Water soluble cleanup before drying.)
Apparently it was or wasn't folded in under someone else's "Roadkill" brand, which used to belong to a competing, more tarry/less useful spray... I never managed to find the stuff, not that I was looking hard, and my current tower is an IBM tank with few noise issues, so it's been less of a personal concern.