Dither and Bit Depth Reduction: What Actually Works
Adding a small amount of noise when reducing bit depth, such as from 24-bit to 16-bit, to avoid distortion from truncation.
Tomas Lindqvist
What is at stake
Reducing bit depth without dither creates harsh quantization distortion in quiet passages, which dither replaces with benign noise.
The playbook
- Work at 24-bit or 32-bit float
- Dither once at the final conversion to 16-bit
- Use noise shaping where appropriate
- Avoid dithering files that stay at 24-bit
- Check quiet fades after conversion
Where it goes wrong
Avoid:
- Dithering several times in a workflow
- Truncating without dither
- Converting to 16-bit early in production
- Assuming dither is needed for lossy codecs in the same way
The numbers behind it
| Measure | Figure |
|---|---|
| When to dither | when reducing bit depth, typically at the final export |
| 16-bit dynamic range | about 96 dB |
| 24-bit dynamic range | about 144 dB theoretically |
| Noise shaping | moves dither noise to less audible frequencies |
Getting outside help
When to hand it over: Bring in help when preparing masters for CD, broadcast or archival delivery.
Where this comes from
- iZotope — Dithering guide
- Audio Engineering Society — Educational resources
The figures and practices above come from the sources listed.
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