For the purposes of this discussion, "power" means the average power or energy contained in a signal over a long period of time. White noise has the same distribution of power for all frequencies, so there is the same amount of power between 0 and 500 Hz, 500 and 1,000 Hz or 20,000 and 20,500 Hz. Pink noise has the same distribution of power for each octave, so the power between 0.5 Hz and 1 Hz is the same as between 5,000 Hz and 10,000 Hz. Since power is proportional to amplitude squared, the energy per Hz will decline at higher frequencies at the rate of about -3dB per octave. To be absolutely precise, the rolloff should be -10dB/decade, which is about 3.0102999 dB/octave.
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