Use the Median Filter command to remove small random specks or areas of noise that are distinctly different from the surrounding area. You can also use the command to remove single-pixel colored specks.
The Median Filter command adjusts the intensity of each pixel in the image to the median intensity of surrounding pixels. The median intensity is the middle value (not the average) in the range of values.
To preserve object edges, the Median Filter command adjusts a pixel that is very different from surrounding pixels more than a pixel that is similar to surrounding pixels. You can choose the number of surrounding pixels to use in the calculation. If you choose a large number, more noise is removed and so more detail is lost.
To remove small areas of noise:
Select the area that contains the specks. See Using the Selection Tools.
Choose Adjust > Add/Remove Noise > Median Filter.
For Filter Aperture, choose the number of surrounding pixels to include in determining the median intensity of each pixel. The filter is always an odd number of pixels. To preserve image details, choose the smallest filter that removes the noise. For single-pixel colored specks, set the filter to 3.
Click OK.
Removing Multiple-Pixel Black and White Specks
Removing Noise While Preserving Edge Details
Removing Noise While Preserving Texture Details