Grey noise

Not to be confused withInternet background noise.

Grey noiseis random noise whosefrequency spectrumfollows anequal-loudness contour(such as aninvertedA-weightingcurve).

Grey noise spectrum

The result is that grey noise contains all frequencies with equalloudness,as opposed towhite noise,which contains all frequencies with equalenergy.The difference between the two is the result ofpsychoacoustics,more specifically the fact that the human hearing is more sensitive to some frequencies than others.

Since equal-loudness curves depend not only on the individual but also on the volume at which the noise is played back, there is no one true grey noise.A mathematically simpler and clearly defined approximation of an equal-loudness noise ispink noisewhich creates an equal amount of energy per octave, not per hertz (i.e. a logarithmic instead of a linear behavior), so pink noise is closer to "equally loud at all frequencies" than white noise is.

Inverse ITU-R 468 weighted "grey noise"

See also

• Colors of noise