Earlier quoted context omitted.
> restaurants can have good sound design, but it doesn't come cheap. Carpet the ceiling and the walls. Super cheap, super effective. Ideally carpet the floor too - and if you use carpet tiles then when a customer spills something uncleanable on a tile it's a 5 minute non-expert job to pull up a tile and put in a new one.
> Carpet the ceiling and the walls. Super cheap, super effective. Super dangerous and illegal, too. The reason that professionals don't do this is because no one will permit it, not because there's some scam on acoustic foam and diffusers... well there is but it's not the acousticians' fault. It's a massive fire hazard.
You mean we haven't figured out a material that both dampens sound and is fire resistant?
Being as how the former quality is pretty easy, I find this hard to believe.