Hi Hans,

    Well, it's not free, or even cheap, but the MATLAB NN simulator is
pretty good and it does run on all major platforms. There is a huge user
base, and lots of people make their MATLAB code available. You can also
read, write and play sound files from within the MATLAB environment
making it handy for development. If you have the compiler, you can
generate C (or C++ code) from MATLAB and then include it in a C language
project.
    I am not sure exactly what you have in mind, but from my experience,
getting the right feature vectors for your classification or
identification job is a big part of solving the problem. MATLAB has all
kinds of signal processing and statistical "feature extractors" in the
two respective tool boxes that can be of help.
   The Stuttgart simluator is pretty good, but because it lacks the
commercial support, you are considerably more likely to bump up against
bugs that are difficult to track down. Of course, you can't beat the
price.

- lonce wyse