The DVI input that you are using does not carry sound. You would have to funnel that through one of the normal AV connections.
If your TV is HD ready,
Lets say you have DTV linked to AV2. There should be an entry HDTV uunder connection AV2 where you can switch to the DVI port. Funnel then the sound through AV2 and the picture through DVI.
otherwise I agree its off to component connnection.
BS9000, BS2300, BC2, BL2500, BL3, Bl2, BS1, BV8, BC4, A8