[cimmanom]

A lot of offices have a culture where headphones-on means "do not disturb" or "slack to see if it's ok before disturbing".

You don't even have to play music if you don't want to - just put a pair of cheap headphones on your head.

[kreeWall]

This is my advice too - I usually don't play music in my headphones, but then I can ignore people when they're talking to me for the first couple of seconds, and then i can look up and they have to start over. It's mean, but effective.