After we published “Pink noise with all high bits“, today brings two calibration sounds for left and right channels with 20 Hz to 20 KHz.
Pink Noise (20 Hz to 20 KHz) Left Channel Only
Pink Noise (20 Hz to 20 KHz) Right Channel Only
Pink noise or 1/ƒ noise is a signal or process with a frequency spectrum such that the power spectral density is inversely proportional to the frequency. In pink noise, each octave carries an equal amount of noise power. The name arises from being intermediate between white noise (1/ƒ0) and red noise (1/ƒ2) which is commonly known as Brownian noise.
Pink Noise Description (wikipedia)
There is equal energy in all octaves (or similar log bundles). In terms of power at a constant bandwidth, 1/ƒ noise falls off at 3 dB per octave. At high enough frequencies 1/ƒ noise is never dominant. (White noise is equal energy per hertz.)
The human auditory system, which processes frequencies in a roughly logarithmic fashion approximated by the Bark scale, does not perceive them with equal sensitivity; signals in the 2–4-kHz octave sound loudest, and the loudness of other frequencies drops increasingly, depending both on the distance from the peak-sensitivity area and on the level. However, humans still differentiate between white noise and pink noise with ease.
Graphic equalizers also divide signals into bands logarithmically and report power by octaves; audio engineers put pink noise through a system to test whether it has a flat frequency response in the spectrum of interest. Systems that do not have a flat response can be equalized by creating a “mirror image” using a graphic equalizer. Because pink noise has a tendency to occur in natural physical systems it is often useful in audio production. Pink noise can be processed, filtered, and/or effects can be added to produce desired sounds. Pink noise generators are commercially available.
From a practical point of view, producing true pink noise is impossible, since the energy of such a signal would be infinite. That is, the energy of pink noise in any frequency interval from ƒ1 to ƒ2 is proportional to log (ƒ2/ƒ1), and if ƒ2 is infinity, so is the energy. Similarly, the energy of a pink noise signal would be infinite for ƒ1 = 0.
Practically, noise can be pink only over a specific range of frequencies. For ƒ2, there is an upper limit to the frequencies that can be measured.
In the feature we publish other pink noise sounds for professional audio systems.