The wavelet denoise plugin is a tool to reduce noise in each channel
of an image separately.

The default colour space to do denoising is YCbCr which has the
advantage that chroma noise can be reduced without affecting image
details.  Denoising in CIELAB (L*a*b*) or RGB is available as an
option.

The user interface allows colour mode and preview channel selection.
The denoising threshold can be set for each colour channel
independently.

The plugin can be found under "Filters > Enhance > Wavelet denoise"

WWW: http://registry.gimp.org/node/4235