A system and method for selecting an audio source is disclosed. The system and method can be used to prevent the selection of a hard disk drive as an audio source if the local ambient pressure in which the motor vehicle is operating is less than a predetermined pressure. The system may obtain ambient pressure data from various different types of sensors including a barometric pressure sensor or an engine combustion sensor. In some cases, the system and method can compute the ambient pressure using global positioning system (GPS) information.