The emulator is slow because it is using a software rendering pipeline, and then sending each frame through JNI to be drawn with the ridiculously slow Android API. I expect it will run most games at a playable speed once I've ported the OpenGL render to GLES. I'll be tackling this after I add the audio linkage, but this will not be an easy project (it will take some time to get it running properly)
There is no sound, because Android doesn't ship with SDL or OpenAL, which are the two audio pipelines written into Yabause. I have written an Android port of OpenAL (called ALAN) which I may use, or I could port the SDL pipeline to SDL 1.3 and use the official Android port of SDL, or (preferably) I could write a new audio pipeline for SLES, which would be fastest.