Dodge DURANGO 2017 Owner's Manual page 190

188 UNDERSTANDING THE FEATURES OF YOUR VEHICLE
If an obstacle is detected in the left and/or right rear
region, the display will show a single arc in the left and/or
right rear region and the system will produce a tone. As the
vehicle moves closer to the obstacle, the display will show
the single arc moving closer to the vehicle and the tone will
change from a single 1/2 second tone to slow, to fast, to
continuous.
Slow Tone
Single 1/2 Second Tone