Logic Pro includes 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). Dithering can be used when:
Burning audio files to a CD
Bouncing audio files to disk
Exporting AAF files (See Export a project as an AAF file.)
The following dithering options are available in the Bounce dialog:
None: No dithering is applied.
POWr #1 (Dithering): A special dithering curve is used to minimize quantization noise.
POWr #2 (Noise Shaping): Additional noise shaping is used over a wide frequency range, which can extend the dynamic range of the bounce file by 5–10 dB.
POWr #3 (Noise Shaping): Additional, optimized noise shaping is used, which can extend the dynamic range by 20 dB within the 2–4 kHz range (the range in which human hearing is most sensitive).
Note: Noise Shaping minimizes the side effects caused by bit reduction (downsampling), by moving the quantization noise spectrum to the frequency range above 10 kHz (the least sensitive part of the range of human hearing). This process is technically known as spectral displacement.
UV22HR: Allows for the best possible sound resolution when bouncing 24-bit recordings into 16-bit files.
The dithering algorithm that sounds best depends on the audio material, and also your personal taste. Audition the audio material to be dithered with each of the algorithms to determine the best setting. In some cases, you may find that the best results are achieved by using no dithering at all.
Important: Avoid dithering the same audio signal multiple times.