Audi False Alarm
This bulletin applies to 2006 Audi A4, S4 and RS4 models. After opening the vehicle door, a slight hissing sound can be heard from all speakers even though the radio is switched off.
The radio amplifier is activated as soon as CAN bus communication is started. This is to allow for navigation and telephone audio even with the ignition off.
The hissing noise is superimposed by other sounds when driving.