Dodge Durango 2012 Owner's Manual page 256

254 UNDERSTANDING THE FEATURES OF YOUR VEHICLE
The system will indicate a detected obstacle by showing
three solid arcs and will produce a one-half second tone.
As the vehicle moves closer to the object the EVIC
display will show fewer arcs and the sound tone will
change from slow, to fast, to continuous.
Park Assist System OFF
Slow Tone