RA (RealAudio) is an audio format released in 1995 by RealNetworks. It uses multiple audio codecs, including high-fidelity music formats and low-bitrate formats. Since its introduction, the RA format has been mainly used by radio stations to stream audio online. Also, up until 2009, the BBC has been using it to stream sounds online.
RealNetworks RealPlayer Cloud VLC Media Player Wensites with the RealPlayer Plugin
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.