With these on bedroom walls it shows you mean business with music.
A the same time buying these I got Auralex mopads to see how this foam compares to a lot more expensive name brand foam and honestly up close they look nearly identical and are nearly identicaly squishy to touch.
As for effect on room sound I can't say I notice a big difference, maybe tiny slight difference is audible in room next to mine. So definitely thinner ones are pointless. (My bedroom doesn't have any echo or anything like that, I have furniture like closet and bookcase on two walls, window on third, and on fourth just bed so whole wall above it empty, that where I put these.) If I could afford those over four times more expensive and I would get them, and they would be as effective as those I would be peeved, you can't return somethig like that that you glue to the wall, but these are deffenetly worth the price, best size to price ratio I could find anywhere.