Noise Effect; Noise Alpha Effect - Adobe AFTER EFFECTS 7.0 Manual

ADOBE AFTER EFFECTS 7.0 472
User Guide
This effect works with 8-bpc and 16-bpc color.
Original (left), and with effect applied (right)

Noise effect

The Noise effect randomly changes pixel values throughout the image. The layer's quality setting does not affect
Noise.
This effect works with 8-bpc, 16-bpc, and 32-bpc color.
Original (left), and with effect applied (right)
Adjust the following controls for the Noise effect:
Specifies the amount of noise, and therefore the amount of distortion, through random
Amount Of Noise
displacement of the pixels. The range is 0% (no effect) to 100% (the image may not be recognizable).
Randomly changes the red, green, and blue values of the image's pixels individually when Use Color
Noise Type
Noise is selected. Otherwise, the same value is added to all channels.
Determines whether the noise causes pixel colors to wrap around. When the color of a pixel gets as large
Clipping
as it can, clipping makes it stay at that value. With unclipped noise, the color value wraps around or starts again at
low values. When Clipping is selected, even 100% noise leaves a recognizable image. For a completely randomized
image, turn off Clipping and turn on Color Noise.

Noise Alpha effect

The Noise Alpha effect adds uniform or squared noise to the alpha channel of a source layer.
This effect works with 8-bpc color.
Original (left), and with effect applied (right)