The speed at which sound/speech is played should be adjustable without noticeable reduction in the sound quality. A choice between a male or female voice may be an advantage.
The possibility of recording speech would motivate interaction. This function would also allow helpers to add extra information/help.
Auditory information is used in different ways: for messages, effects (not necessarily important for the game itself), interaction with the user, ...It is an advantage if the various types of auditory information can be adjusted individually (see 4.2 Sounds e.g. background music and alarms that can be switched off/on).