Unfortunately, the Z80 has not been emulated yet, and that's the chip that usually does the sound. Other games use a different chip (the 68000 IIRC) some games (like Sonic 1 and Streets of Rage 1&2) use that chip so you get sound.
Yeah there's not many games that work with sound, hopefully it won't be long before the Z80 is emulated, but since I don't usually have the sound on anyway as I usually play at work no big deal.
M64 FIRSTPLAYER - use the search function FGEN32 and Giga Drive both work well.