Just some facts I dug up using google. Thought it was interesting.
"Pink noise has a spectral envelope that is not flat within a frequency but rolls off at higher frequencies. Pink noise has a greater relative proportion of low frequency energy than white noise and sounds less “hissy.”
For the human auditory system - which processes frequencies logarithmically - pink noise is supposed to sound even across all frequencies, and therefore best approximates the average spectral distribution of music.
In practice though, it turns out that our ears are more sensitive to certain frequencies, such as in the 2–4 kHz range. Pink noise, despite of its even frequency distribution in the logarithmic frequency scale, will therefore be perceived as colored, with a prominent peak perceived around 3 kHz. Flattening a noise in a perceptual way, will generate grey noise
Applications
In audio applications, pink noise is used as a reference tone to check frequency responses and becomes particularly useful when coupled with a 1/3 octave spectrum analyzer.
This type of analyzer operates with a constant percentage bandwidth, which means that the bandwidth of its filters gets wider toward the high frequencies. As the filters get wider, the power of the source signal should decrease, to keep the readings correct, hence, the use of pink noise. If your spectrum analyzer does operate on a constant bandwidth (not a constant percentage), use white noise instead.
Pink noise can be used to measure the adverse effects of room modes as well, although a low frequency sine sweep will be better for such a purpose.
In healthcare applications, pink noise is used to treat hyperacusis, an increased sensitivity to normal environmental sounds, or to mask tinnitus, a ringing in your ear occurring without any stimulus."