xspectrum is a program that displays the spectrum of the soundcard's input signal, in the form of a waterfall display. It should run on any Unix system with X11 and the OSS sound driver, but so far it has only been tested with Linux. You will also need GTK+ 1.2 and fftw.
More information kan be found in the man page or in the INSTALL file. Or, have a look at some screenshots.
Xspectrum comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to redistribute it
under the terms of version 2 of the GNU General Public License.
You can download xspectrum version 0.1 at http://www.scintilla.utwente.nl/~vincenta/xspectrum/xspectrum-0.1.tgz