AP3 file format is a VS10XX VSOS App from Asprova – an APS (Advanced Planning and Scheduling) system for Microsoft Windows OS. In short, it saves the scheduling project created via Asprova. Naturally, other apps can use files with .ap3 extensions. Just be cautious with AP3 data from unknown sources.
AU is an audio format standard in early web pages NEXT systems. It is also called u-law or Sparc-audio format. Typically, AU files can store audio data and annotation blocks. Initially, it was a headerless audio format, but newer versions have a header, thanks to the six unsigned 32.bit words.