Sound will get into every nook and cranny it possibly can. That's a pretty cool property but sometimes it can be annoying.

Take my apartment door: there's a fairly even 1/4 inch gap around the whole door for sound to travel through. At least the door frame juts inward on the outside of the door to block direct noise but the gap around the door is preserved by three small rubber stoppers (marked in red).

Their function is probably to stop the metal door from banging on the metal door frame but they also hold the gap there, allowing sound to travel in from the outside and out from the inside.

It would be nice if I could fix this gap and cut the noise travel so I don't disturb my neighbors when I play my John Tesh records at full volume. By the same token I'd rather not be woken up by my neighbor across the hall jingling his keys at 6AM.

So I'm thinking of replacing the three stoppers with a rubber strip of the same width, going completely around the door frame (B). If that doesn't block most of the noise I could also add a small piece of plastic or rubber to the inside of the door (A).

This may be a little silly, sure. :) But a little bit of work could cut down on a lot of noise so I don't disturb my neighbors and the hallway noise doesn't disturb me.