Hi, I’m Fyn. Sound engineer in Portland, OR. Into retro computing (mostly 80s home computers), mechanical keyboards, and climbing. I’ve been around the fediverse a while now (Mastodon - @fyn@mstdn.party) and wanted a home on the forum side of things. Nice to meet you all, and happy to answer any questions.
It depends what kind of sound.
In general though, you heard right. There is a product called “mass-loaded vinyl” that I used (by soundsulate, I think) between TV and my wife’s study - but if you have access to the wall cavity, rockwool is very good
Careful just adding rockwool to an outside wall though. Potential mold factory if vapor barrier and such isn’t correct as it’ll trap moisture and heat.