this is a neat tidbit. mycelial fungus has been adapted for creating an eco-friendly sound proofing material. and (shameless Star Trek Discovery plug) the bonus is the ability to travel anywhere in the galaxy when bored!
If I am not mistaken, you want density and mass when it comes to soundproofing — this is because you do not want the sound to get out, and vice-versa. Nowadays, soundproofing mats are highly popular. They are very thin, but are extremely dense and heavy… and also have a nice price tag on them.
I have always thought about utilizing sand for sound-proofing, it’s quite heavy and perhaps it could be put to use.
Just a thought
I am sure people found a number of DIY ways to soundproof
soundproofing takes many forms…this one copies the theory used in silencers I believe, where the sound is deflected / reflected upon itself but never escapes so it eventually runs out of energy.
If it does get implemented in walls, I’d question whether it would degrade etc.
But otherwise a very nice concept