A random-like signal in which power is proportional to the inverse of frequency. At twice the frequency, we would expect half the power, which is a 3dB decrease. This is a frequency-response slope of -3dB / octave, or -10dB/decade. As opposed to white noise, which has the same level at all frequencies, pink noise has more low-frequency or "red" components, and so is called "pink".
Due to this roll-off, pink noise sounds less bright and richer in low frequencies than white noise.
Narrow band analysis will show a fall in level with increasing frequency, but third-octave band or octave band analysis will be flat.
Pink noise is often produced by filtering white noise and has the same power within each octave.
As pink noise has the same energy in each 1/3-octave band, it is the preferred sound source for many acoustical measurements due to the critical band concept of human hearing.
See also: White Noise.
Subjects: Noise & Vibration