Auto Volume Control
WARNING: This page is about a different car, the 2011 Chevrolet Volt. However, it is still accessible from the selected car via links, so may be relevant.
A microphone mounted in the vehicle passenger compartment monitors background noise (such as changing road surfaces, driving speeds or open windows). The radio modifies the system's volume and equalization to minimize the effects of unwanted background noise based on the user setting.
Available selections are: OFF, Low, Medium, or High sensitivity.