Sound can be activated using the -dsp switch after running the executable from your terminal (MS-DOS Promp, Xterm, etc).
Concerning speed. We know that VJ/SDL is a bit slow but it's still work in progress. Optimisations on something on our (very long) TODO list

But keep in mind, the Jaguar is a very sephisticated piece of hardware/console and emulation won't be speedy at best!