Definition(en): Covox ADPCM Audio Files (also known as Covox 8-bit audio) is a title for a family of Adaptive Differential Pulse Code Modulation (ADPCM) formats, used for compressing 8-bit unsigned pulse code modulation. They were invented by Covox for use with Covox sound output devices. ADPCM is a lossy compression format containing audio data that are optimized for storing digitally recorded or sampled voice data.