Ever heard of Mathlab (http://www.mathworks.com/
), it seemed to be one of the favorite tool for Signal Processing, especially for simulation. The version I used was version some what 5..6 sorry. It run on window and many commercial unixes platforms. Dun know wether it run under Linux.
Signal processing seemed to be a little out of topic in LQ, but am also a fan of it, if u ever found a better Forum, reply to this thread, I'll keep an eye or 2 on this