Dither is a small, deliberately added noise applied just before audio is reduced to a lower bit depth — for example when a 24-bit mix is rendered to a 16-bit master. Without it, quantization error correlates with the signal and becomes audible distortion that is worst on fades and quiet passages. Dither randomizes the rounding so the error becomes a steady, benign noise instead, preserving detail below the least significant bit that would otherwise be lost. Noise-shaped dither pushes that noise into frequencies the ear is less sensitive to, lowering its perceived level. The rule of thumb: dither once, at the final bit-depth reduction, never repeatedly.
