Sound II Reading

Pink noise

each octave carries an equal amount of noise power. For the human auditory system - which processes frequencies logarithmically - pink noise sounds evenly spread across all frequencies and best approximates the average spectral distribution of music.

White noise 

power distribution is flat across the entire frequency range. In other words, white noise contains all frequencies in equal proportion. For the human auditory system - which processes audio in a logarithmic frequency scale - white noise sounds much brighter than pink noise.

A simpler way to think about the difference is to relate pink and white noise to the Equal-loudness contour curve. Pink noise is all is frequencies of 20 Hz to 20 kHz at the same power level, so we hear this as a mid-range sound since the Equal-loudness contour curve tells us our perception when listening to frequencies at the same perceived volume level will cause the low and high frequencies to roll off leaving mostly mid-range frequencies.

White noise is all the frequencies of 20 Hz to 20 kHz at the same perceived level. This means white noise factors in compensating for our hearing and boost the level of low and high frequencies so we perceive the loudness of each frequency to be the same. Since we now can hear all the frequencies, this will make white noise brighter.