The Noise of Pink

I was aware of the fact that you could use music to drown out annoying noises, but the fact that you could use natural noises to lessen it's impact was surprising, mostly because annoying noises are alot louder than natural noises and tend to be quite a bit softer.
Perception vs. Concentration
I believe that this would be a situtation where our perception effect our ability to concentrate. The loud noises are percieved easier and so is more apparent and distracting, while the addition of "pink noise" or music, allows it to be complicated and more enjoyable, allowing you to concentrate easier on whatever you're doing.