to Cable Forum
A standard scart lead carries the rgb signal, and audio, along with a couple of other signals, i.e. the tell your TV to swithc to AV channel 'cos the STB is on.
It will depend on your audio device how sound is best received. If you are talking home cinema, most of these will have phono sockets. The best way is to get a break out Scart lead. This will have a standard scart plug at either end, but also a set of phono plugs that you can then extend and connect to your hi-fi