AMR (Adaptive Multi-Rate Audio Codec) is a sound compression format that is designed for speech coding. It is today widely used in UMTS (Universal Mobile Telecommunication System) and GSM (Global System for Mobile Communications). Most modern mobile phones can save short sound recording clips in AMR format and can be converted to other standard sound formats using a third-party program like Wondershare UniConverter.
AMR Player Mplayer VLC Media Player QuickTime Player
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.