Some other pages on our site you may enjoy:
RTSPECT - Real-time Waveform and Spectrum Display
RTSPECT is a free program for displaying a real-time waveform and spectrum display of an audio signal on Windows computers. More information.
ESYSTEM - Signals and Systems teaching tool
ESYSTEM is a free program for experimenting with signals and systems. With ESYSTEM you can see the effect of simple systems on a range of simple signals. More information.