Logic Express provides you with the professional POWr (Psychoacoustically Optimized Wordlength Reduction) and UV22HR dither algorithms, designed to convert 24-bit recordings to 16-bit files (as required for CD burning, for example).
POWr dithering can be applied when:
Bouncing audio files to disk
Exporting OMF files (See Exporting OMF Files.)
Exporting AAF files (See Working with AAF Files.)
You can choose between the following dithering modes:
Note: Noise Shaping minimizes the side effects caused by bit reduction. It does this by moving the quantization noise spectrum to the frequency range above 10 kHz—the range the human ear is least sensitive to. Technically, this process is known as spectral displacement.
The dithering mode that sounds best to you is primarily dependent on the audio material, and your personal taste. Audition the audio material with each of the dithering modes to determine the right setting. In some cases, you may find that the best results are achieved by using no dithering at all.
Important: Dithering the same audio signal multiple times should be avoided.