The Anti-aliasing Filter is a low-pass filter used at the input of an A/D (Analog-to-Digital) converter to prevent distortion known as aliasing.

The job of the Anti-aliasing Filter is to block any frequency higher than this limit at the input. It does this by applying a very steep cutoff at the end of the audio spectrum, ensuring that no sound beyond that enters the converter.

By removing these excessively high frequencies before conversion, the filter prevents the converter from becoming confused and creating the inharmonic "ghost frequencies" that characterize aliasing, ensuring a clean and artifact-free digital conversion.