SoundConverter is a simple sound converter application for the GNOME environment. It reads sound files in any format supported by GStreamer and outputs them in Ogg Vorbis, FLAC, or WAV format, or MP3 format if you have the GStreamer LAME plugin.
SoundConverter aims to be simple to use, and very fast. Thanks to its multithreaded design, it will use as many cores as possible to speed up the conversion. It can also extract the audio from videos.
Installation in Ubuntu
SoundConverter is default available in Ubuntu official repository, just search and install it in Ubuntu Software Center. Then find it under Applications -> Sound & Video menu.
In this clean and easy interface, click Add File or Add Folder and then click Convert to process single or multi files.
Before this, you may need to change output preferences under menu Edit -> Preferences