Soundproof Walls - How well do soundproof walls work?

How well do soundproof walls work?

If I was to play guitar really loud or have a band come in and play with soundproof walls, how well would it block the sound, would you be able to hear it outside just barely?. or would it shake the walls outside?

Public Comments

Truly SOUNDPROOF walls are made of a special material to do the job. It's not a cheap job but done properly you won't be heard outside nor will it shake the walls. If the room is on a second story then the floor would have to be sound proofed too. Good luck.
Home Depot sells sound board for sound proofing walls. And, it's cheap too.
if you can hit a wall without hearing a loud bang or vabration then its sound proof. thing concrete blocks or thick steel walls are perfect and perfect sealing. ant sized gaps always let sound escape. that is if you don't want people to hear you outside. but if you just want to reduce the noise and echo, uneven surfaces would be good, wall material that look like those old fashion egg cases