The Safe and Sound Drive project concerns the design of an audio-only serious game for cars that will help drivers to increase eco-driving skills, lower fuel consumption and encourage safe and environmentally friendly approaches to driving. Methods and procedures for the design of sounds for audio-only user interfaces are reviewed and discussed, and design work and preliminary results from user studies of prototypes of the audio interface are presented. Contextual Inquiry Interviews with three participants using the audio interface in a car while driving on a test track showed that opinions about beeps and audio signals vary among subjects. Music and podcast based contents were generally well received. Alteration of media content, e.g. by actively adjusting BPM, volume, spectral balance, or music mix could form working mechanisms for providing game related cues to the driver.