I'm in need of a function generator, but I want to avoid buying dedicated laboratory instrument. My idea is to use computer's sound card to create signals (yes, I know that it's not a replacement for the real thing). I'll most likely need just simple sines, squares, sawtooths and similar.
So I'm looking for a program which can generate waveforms and should work on windows 7 or Ubuntu 10.04. If it's free software, then it's a plus.
To me Audacity looked like obvious solution, but I'm hoping that there is a program which can display how the emitted wave looks like and can generate sound in real time (I know that shape of the wave can be solved with a prerecorded audio and clever visualizations).