Sound waves are just like light wave, they have a lot of the same behaviors, they reflect, deflect and diffract, and the bathroom has some features a living room doesn't have: bathrooms are usually empty, it helps sound to reflect and bounce from wall to wall without randomly-shaped obstacles that diffract it - in case it was solid - or absorb it - if it was soft like clothes, sofas, curtains .. etc, also, bathrooms are small, so sound waves can travel among walls for more times before they fade away (actually they transform into heat because of friction).
Other important feature a bathroom has is its shape, which is usually rectangular or square shape, and by having parallel walls sound waves get reinforced when they bounced among two parallel walls (even they mute sound suddenly when a wave's peak meets its bounced valley), and that is why all professional recording studios or recording booths have tilted walls, not parallel.
Finally, It depends also on the song, if it is a cool song, you will be more happy :D