I believe audacity is capable of running vst plugins, which is what you will require to manipulate your sound bytes.
The type of plugin you are going to need is called a sampler. Basically, it opens up inside audacity and will allow you to load a sample into it and the apply any number of effects, filters, etc.... To create new sounds. A very powerful inbstrument. There are a lot of free ones out there, many of them used to be commercial products until they were superceded by better plugins so you know you are installing good quality products. One to try furst off would be shortcircuit from vemberaudio.se it should be enough to get you started for no outlay and then you can decide if this is the direction you are wabting to head in.
Good luck.