Aglaophone is a system of interconnectable modules for the recording, processing, and playback of real-time audio. It features a real-time spectrogram display for visualization along with a number of processing modules. Modules include filters, downsamplers, upsamplers, and quantizers. An MP3 comparison module allows interactive blind comparison of MP3 encoded audio with CD audio, demonstrations of spectral imaging, quantization, and Smith-Barnwell filter bank based wavelet decomposition are included, and there is a module that can perform an automatic spectral analysis of a speaker system.
eXtace is a visual sound display/analysis program. It requires Esound (esd) for its audio source. It includes various fast fourier transforms of the audio data in realtime. Its displays include a 3D wireframe flying landscape, a 3D textured flying landscape, a 16-256 channel graphic EQ, three types of scopes, a 3D "spike" flying landscape, and two forms of spectragrams. The 3D traces can be picked up, manipulated, and displayed at nearly any angle. eXtace also features a 3D direction control widget for controlling the angle and speed at which the trace runs away and a gradient/colormap editor for changing the colormap to suit your needs. No OpenGL is required.
HASAS (HydroAcoustic Signal Analysis System) is a modular system for passive sonar signal analysis. It can be used for biological research or surveillance, for example. The soundcard is used as input device, and it currently includes all the very basic functionality; beamformed audio, direction finding, level histogram, LOFAR/DEMON (narrowband spectrogram), wideband spectrogram, and raw audio.
Synaesthesia is an eyecandy program that represents music graphically in real time as coruscating fields of fog and glowing lines. It is intended as a visual accompaniment to music. Its display combines information about the frequency, location and diffuseness of sound. It can take input from CD, line, piped from another program, or from EsounD. It also functions as a CD player.
Waterfall is a visualization plugin for XMMS. It's yet another spectrum analyzer, but it presents the data better, which makes it more interesting to watch. Most analyzers show a changing 2D bar graph of frequency vs. intensity. This one shows a scrolling 4D plot of frequency, time, intensity, and a configurable fourth variable mapped to hue.