Grey noise

Random noise whose frequency spectrum follows a psychoacoustic equal loudness curve

This article has multiple issues. Please help improve it or discuss these issues on the talk page . (Learn how and when to remove these messages)

This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed.
Find sources: "Grey noise" – news · newspapers · books · scholar · JSTOR (February 2025) (Learn how and when to remove this message)

This article may contain excessive or inappropriate references to self-published sources . Please help improve it by removing references to unreliable sources where they are used inappropriately. (February 2025) (Learn how and when to remove this message)

(Learn how and when to remove this message)

Colors of noise
White Pink Red (Brownian) Purple Grey
v t e

Not to be confused with Internet background noise.

Grey noise is random noise whose frequency spectrum follows an equal-loudness contour (such as an inverted A-weighting curve).

Grey noise spectrum

The result is that grey noise contains all frequencies with equal loudness, as opposed to white noise, which contains all frequencies with equal energy. The difference between the two is the result of psychoacoustics, 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 is pink noise which 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.^[1]

10 seconds of grey noise