GLAME. Welcome to the wonderful world of GLAME, short for GNU/Linux Audio Mechanics! The project aims to present you with a powerful, fast, stable and easily extensible sound editor for Linux and compatible systems. And best of all, it's GPLed!
ReZound aims to be a stable, open source, and graphical audio file editor primarily.
Sweep is an audio editor and live playback tool for GNU/Linux, BSD and compatible systems. It supports many music and voice formats including WAV, AIFF, Ogg Vorbis, Speex and MP3, with multichannel editing and LADSPA effects plugins.
WaveForge is a free sound editor for X. It features several audio effects, a GLADE interface and GNOME support.
SoX, the Swiss Army knife of sound processing programs.
Audacity® is free, open source software for recording and editing sounds.
GNUsound is a multitrack sound editor for GNOME 1 and 2.
Ecasound is a software package designed for multitrack audio processing. It can be used for simple tasks like audio playback, recording and format conversions, as well as for multitrack effect processing, mixing, recording and signal recycling. Ecasound supports a wide range of audio inputs, outputs and effect algorithms. Effects and audio objects can be combined in various ways, and their parameters can be controlled by operator objects like oscillators and MIDI-CCs. A versatile console mode user-interface is included in the package. See key features and technologies for more details.
9. Sound Studio
Sound Studio, a simple light-weight tool for editing smaller soundfiles. Because Sound Studio uses Sox, it can cope with a wide variety of audio file formats. Because it is written mostly in Tcl/tk, it is easily extensible.
mhWaveEdit is a graphical program for editing, playing and recording sound files. It is lightweight, portable, user-friendly and handles large files very well.