I have a computer upstairs in the study which is often used to play music locally. It also hosts a SqueezeServer and streams music wirelessly on request to the SqueezeBox in the family room (== living room, although we don't call it that).

In general if I'm anywhere other than in the study or family room and want music, I set it up to play in the family room and then just turn the volume up :-) I can then listen in the kitchen, dining room, and our bedroom (which is above the family room).

It's a detached house and I have checked that when you are outside, you can barely hear the music emanating from inside even when I have it cranked up :-)