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.
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.
MPEG Maaate (MPEG audio analysis toolkit) is a C++ toolkit to parse and analyse audio data in the frequency domain, e.g. analysing MPEG-1/2 Layers 1-3 audio files in the compressed domain. It makes the encoded fields of an MPEG audio stream accessible and provides some content analysis functions like silence detection.
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.